Dad and I sat down to play a game called "Changes", and didn't read the box. 

When he rolled the die and moved the first piece, it landed on a square that gave him a card that read "turn into a dickgirl so your son can suck your cock".

"What the fuck," he said, and tried to put the game away immediately. He couldn't lift it. He couldn't remove the piece either. 

I read the instructions: "Warning, this is an erotic game and not for play with your family unless you are a sick fuck.  You will have to fuck other players. You must transform."

Dad wanted to say something else, but first he transformed:
 

 Dad fell back to the floor and became the girl you see above. 
"Son, my cock is so hard and leaking," he said in a whiny voice. I could only do what the game told me to do.... I bent down and sucked his cock.
"What, what are you doing?" he said, between moans. His cum began pumping down my throat. 
I grabbed the die and rolled. I made it past his first piece, but not too far past it. I took a card. It said "Join your daddy and become a girl. Get his tongue on your dick like his was on yours".
"What, I'm not going to suck a cock," said my dad, still jerking his own hard dick off. I transformed then too:

"Oh my god," my dad said, while we each masturbate furiously, cum spouting out of us. "I've dreamed of that girl for years."

"What are you admitting, daddy?" I said. He said nothing, but his mouth teased the tip of my dick. I continued cumming  as he took it in his mouth. For a moment I couldn't even remove him, I came harder and harder.
"Fuck, I guess we have to finish this game," dad said. He rolled the die and moved a few more spaces.
His next card said "coule play, close your eyes and accept the surprise". 
I found my eyes closed, and his eyes were closed as well, I think. I felt myself changing, becoming fully female. 
Then, it seemed a third person entered the room. My hands went around my daddy, and pulled him close. I thought we were about to kiss, but that third person became to cum all over our faces.

After the person finished, I opened my eyes. Dad opened his. We were blasted with cum. Something made us start licking each other's face, swallowing the sperm.
Then, I took my next turn. I rolled and came up short, just behind dad's space. "Become daddy's little girl," it said. I transformed again:

I looked up at my father, who was in his own body again. His cock was rock hard.

"Daddy, I'm a girl," I found myself saying.
"I don't... I don't even care that you are my son inside," he said. "This is another fantasy of mine." He pushed me down on the bed, then kissed between my legs. Special kisses that sent butterflies through me.
"This won't really hurt," said daddy. "It'll actually feel good, okay baby?"
"Kay, daddy," I said, wanting to please him. I whined and began to moan when papa's cock thrust into me. But I was soon disappointed: after his intial thrust, his cum shot through me.
"Damn it," dad said, and then took his turn. He transformed now, and I changed back. 
 "Shit, daddy," I said, "you're like the grown version of the girl I just was."
"I'm the mommy version," he said, proudly showing me his baby bump. I reached out to touch it.
"It's yours," he whispered. "So you can do anything you want to me as a prize."
I stood there for a moment, trying to decide what to do. I settled for caressing him, sucking his tits, and then gently entering him missionary style.
"You're such a tender lover to your pregnant daddy," he said. "I love you."
That was what made me cum.
He smiled and told me to roll my next die. "Go ahead, baby."
My dad was calling me baby! My cock hardened at the thought. I took a card and transformed, though dad did not tturn back.

"Oh," dad said, his tongue hanging out of his mouth," you're my wife."
"Yes," I said, "and you're my still pregnant wife." Our hands met, meshed together, melded. We pulled each other into an almost kiss, our faces not quite meeting. Dad's fingers dropped and probed my pussy, gently brushing past me, teasing...
And then he rolled his die.
"Good father's give suck," the card said, and he transformed once more. 
So did I, becoming my former self again.
 "This feels differnet now," dad said. "Like I'm your wife, or girlfriend trying to please my man." And he started gingerly, slowly, licking the head of my cock. I almost came right there. Then he began to push my member into his mouth...
I was about ot cum, so I rolled the dice. The card had me transforming immediately. 
"Become a secret crush of your fathers," the card said. So I did:

I turned into my sister.
"Dad?" I asked.
"What?"
"What is your secret desire?"
"You see what it is, don't you," he said, transforming back into himself."
"My sister?"
"Yes."
"Your daughter?"
"Yes."
"You sick fuck," I said, but approached him all the same. I got down on my knees and wrapped my tits around his cock, rubbing him until he was hard. Then I gave a teasing lick, a tongue up and down his shaft, and then... then I bent over my sister's body snd begged dad to pound me hard. And he did, his cock slipping in and out of me until I thought there was nothing else in existence but this fucking.
Though it seemed a long time, it ended, and dad sat down. He started crying.
"No need for that, dad' I said. "This is a fantasy game, after all. It can't be real."
He nodded, and I licked his tears as he rolled for his next change. 
"Look, drool, but don't touch," said the card. "If you do, there will be a pentalty." With that, Dad transformed into a girl I'd had a crush on.

I couldn't help it. I reached out to touch her, pulled my dad into a kiss.
The board made a buzzing sound.
"Penalty!" a card said-- it nearly flew into my hand. "Two transformations!"
So there was the first... 

I turned into grandma. Dad turned back into himself and... I don't know what came over him. He pushed me down, said "mommy it's time to get your son's dick deep," and thrust into me. I struggled at first, but it felt so good, I just kept moaning and moaning until he came.
And then I transformed a second time...

I think dad was more surprised than me at this transformation. I was fully female, but I had a fake cock strapped onto me!
"How is this punishing you?" dad asked.
"Because I have to fuck you... since your cock is too small for this woman's body." I pushed dad over and roughly began fucking his asshole. As I had just been moaning, he was soon moaning as well. He came in my hand, and I bid him roll the dice.
I found myself transforming back, while dad became female again.

"I need your cock in my mouth," dad said. "Come on, baby."
"But--"
I got no further. Dad grabbed my cock and thrust it against his tits, making sure it was hard. Then he licked my cock with his new tongue in a way that made me cum all over his pretty face before it even got in his mouth. He flashed me the peace sign. 
It was my turn to transform, and I became a girl with a strap on again.
 Dad was about to complain about not getting to suck my cock, but instead... he jumped on my new plastic one. He did most of the work, writhing up and down and up and down until he squeaked and came and came again.
He rolled his die, and picked up a double card.
"Fuck the club, girls," the card said. We both transformed again. 
With our new bodies, and in the middle of a club, we decided it was time to just get to work. We each took a side of the room. I watched as dad got himself stuffed with three cocks in his asshole, two in his pussy, and three in his mouth. I was about to say something to him about it, but men unzipped their pants around me and began whacking my face with their cocks. I sucked them, until all of the men came all over me.
Then dad and I switched places, until we were both left behind in other people's juices. I saw the board, and rolled the die. 
I took my card. It just said "Aunt Karen:. That was my dad's sister.
I transformed.
Dad was back to his own form.
"I've wanted this for a long time, sister," dad said. But when he unzipped his pants, he had already cum. I put my hands up and tried not to laugh.
"Roll your dice," I said. He did, and it was my dad's turn to transform into a fantasy.
Dad literally turned into mommy:
My dad took ym mother's form in front of me.
"You suck little shit," he said, something of his original self come through.
"Like you didn't fantasize about fucking your sister and daughter," I shot back. 
My own cock was hard, and he big me approach. I was in his hands and I came right away as well. He laughed. 
"Fine then," I said, and rolled the dice.
"Maybe you'll do better as a girl," the card said. I transformed unto what might have been myself if I was female.
"Mommy," I said to my transformed dad, "I think my boyfriend knocked me up."

"That's okay honey," dad said, "you can be mommy's girlfriend. He kissed my tummy, and I found msyself sucking on mom's neck. He pulled me back down into a kiss, and then pushed me down between his legs to eat his matriarchal cunt.
He rolled his die. 
"Mammary overload," his card read. He transformed:

"Ouch," dad said in his new form. "These hurt my back." 
"I can massage them, daddy," I said. I found I was back in my own body. Dad nodded, and I pushed him over. He couldn't really do much, so I moved his boobs to massage my cock. I kept going until I spent and my sperm coated over dad's tits. 
Then I took my roll.
Dad was back in his own body, and I was now in a girl body. 
He pushed me down, unable to control himself. He thrust in and out of me harder and harder and harder, and when he was just about to cum, he rolled his die.

We tumbled back so that I was underneath him, and he was on top. He transformed.

My cock went rock hard immediately, and I began to suck on his new titties. 
He had a toy in his pussy as well, and moaned while we fucked.
"Shit son, this is jsut right. Your cock is made for my pussy... I need it in me, never leave me."
I slapped his ass and pulled him into a kiss which he refused to break for a long time.
I looked down at the board... I could win. I rolled the dice. The card I pulled said:
"CHOICE TIME! Do you want to set everything back to reality or do you want to be transformers forever?"
...
Well, it's been about a year. Dad and I don't spend much time doing anything else. And just toda I pulled a new card. In the continuing game, we have a mission every day. On today's mission we are mother and daughter and we must get fucked together: