I love how women's body change after becoming mothers. How their hips are wider, their tits are bigger, and they have a little more fat everywhere (even if they are relatively athletic). I find them irresistible... and as of a few months, such is the body of my older sister.
After her partner walked out on her, she (and her baby) started crashing at my place. And two things start happening in such situations: you become closer, and there's also a few accidents. Like she walking in on me naked in the bathroom, or her coming out to get something from the living room in her underwear and not noticing I'm there.
One night, over dinner, the conversation turned towards my apparently non-existent dating life. I told her I did have one, but admitted I was into older women with certain kinds of bodies (I'm 26, for reference. I've dated women as old as 45). She was amused when I told her I was into MILFs, because of the way they looked. She turned red and I went for it. "Many of them feel embarrased of their bodies afterwards, but I think they are sexier". I said. She looked between confused, flattered, uncomfortable and happy. "You look pretty desirable yourself", I said. She didn't stop smiling, but she looked a bit more flustered. "That's not the kind of thing I expect to hear from you" she said, fidgeting, noticeably more flustered. She picked up the dishes, excused herself, announced she was putting the baby to sleep, and went to bed. I went to my room too, and as horny as I was, I started to jerk off, quietly.
I was halfway done when my door suddenly opened. It was her, but I didn't try to cover myself or anything. She climed on my bed and started jerking me off. "Ever since I gave birth no one had told me they desired me", she told to my ear. We kissed deeply, and then I started fingering her. She was wet in no time. We couldn't resist much longer, and we fucked. I fucked her hard and fast, knowing I wasn't gonna last much longer but I wanted her to cum. Shortly after she did, I exploded inside of her. We hugged and kissed, and then slept together (until her baby woke her up, that is). She didn't seem bothered at all that we're siblings and, well, I'm not gonna complain.
Because we've been lovers for a few months now. That first time was the only time I ever came inside her. Not a problem, since she also likes to tenderly suck my dick and drink my cum, or for me to give her rough buttfucks. She says I'm one of the best lovers she's ever had, and I'm happy to oblige.