Family Ties/Fresh meat.
In order to spare you from the trauma of a trail your mother excepts a plea bargain on a lesser charge and is sentenced to 3 years in prison. The prosecutors don't even let you say good bye and you spend the first month in your new home worried that she won't forgive you.
The foster parents that you are placed are pretty cool, they already a have a set of sisters that had been placed with them 6 months ago. Tina, the oldest at 15 and Gina at 13, took a shine to you almost immediately as they had never had a brother. They were placed after being taken away from their dad after he was convicted of turning them into sex slaves.
About a month an half in to your stay at your new home you received a letter from the prison your mom is serving her time.
Dear Timmy, I miss you so bad and I think about all the time. So you can be sure I am horny most of the time. I can still feel your mouth on my nipples and your beautiful cock in my pussy. You are such a great fuck, the best lover I have ever had. Your dad told me that you were placed with a nice family with two other daughters. Have you gotten into their panties yet? It's OK if you do, I want you to have plenty of practice for the next time we get to make love. My cell make is a really cool gal and pretty too. She got a set of knockers almost as big as mine. I have thought about what it would be like to watch you suck on them before you fuck her..., and me. Her name is Jill and she is the niece of the warden but nobody is supposed to know that. So basically gets away with what ever she want and the guards have to put up with it. I think she is fucking her uncle when no one is looking and that's why she can do what she wants. She is also helping me out which is why I could send you this letter. I've told Jill all about you and she really wants to meet you when her and I get out. She likes hearing about the naughty things we have done together while she's eating my pussy or finger fucking me. Yeah we sleep in the same bed after we fuck of course but you're the only cock I want between my thighs. Some how Jill has got a cell phone so I can actually call you some time when maybe your foster sisters are watching you and you can be alone. I want to listen to my baby beat off on the phone and you can listen to me cum for you. Jill might even want to talk to you too. She wants to have a threesome when we get out of here. We are going to fuck you so hard baby. Just write me back at tell me a good time to call. Jill says if we play our cards right we could both be out in less than a year but that still such a long time to go with out you cock inside me. Please write me back love. I am so afraid that you will forget about me while I'm away. I want to hear all the things you want to do to me when I get out of here. I miss you so fucking much. I miss you being on me and inside of me. Write me and tell me when to call I wanna hear your voice. I need to hear you moan my name again. Got to go sweetie, Jill is horny and frankly so am I. I'll look for your letter and can't wait to talk to you. I love you more than anything baby. Mommy
"Ready for round 4 Tim-Tim??" Gina asks as she pops up from under the covers, your now hard cock in her fist. "I told you I could get you hard again."
"Timmy's always ready for another round with his sexy sisters." Tina beams, pressing her self tightly to your side while she rubs her D cup tits against your cheek, trying to coax her nipple into your mouth for you to suck on.
Gina crawls up your body and slams herself down on your cock with a moan. "Timmy put that letter down and squeeze my titties..., you get to talk to your mommy tomorrow after mom and dad leave to go to the store..." She complains as you toss the letter into a drawer before grabbing a hold of her C cups and massaging them.
"We are going to suck your cock the whole time you're the phone with your mommy sweetie.." Tina coos into your ear as you turn your head to accept her nipple into your mouth and begin sucking on it. "Mmmmm, now be a good little brother in finger my cunny..., I want to be almost ready to cream when I fuck you after Gina is done."
Turns out you got placed with a couple of sex addicts. Maybe this year separated from your mom won't be so bad after all.