She Thought She Was A Lesbian

So my twin sister is bi but has a lesbian girlfriend. At least she says that's what she is. Last week my sister was in a car accident and was in the hospital for 4 days. She and I have always been very close and we live only about a mile apart. We get together often and usually still have Sunday dinner together. Our parents died many years ago and all we have for family are each other. Anyhow her girlfriend Annie is really a nice looking woman even though she's 41. She's always been nice to me but is one of those anti man types, or so it seemed. Anyhow the first night in the hospital was a long one but eventually the Dr said my sister will be fine. So I took Annie home to my house because she has no car and my sister's was totalled. We got home around 2 AM totally exhausted. I have a small one bedroom house but it's really nice with lake access etc... So like a gentleman I offered her my bed and crashed on the couch. I woke up around 7ish and had to pee and went into the bathroom without turning any lights on. I was shocked when after finishing my pee and just shook off the dew to turn around and see Annie there. Even there was little light to see by I could see her pretty well, completely naked. I already had a half hard on which started growing once I saw her. She's only just over 5' tall with small tits but they were nice with big nipples pointing straight at me.
I apologized for seeing her this way but she said it's no big deal. Then I though she was just going to walk by me and sit down to pee but she grabbed my dick. I was really shocked. But I didn't move. Ummm Annie what are you doing? Well Mark you have a nice one and I don't know why but I had to feel it. I said well you have beautiful tits if we are going to compliment each other. We both laughed and she let go and sat to take her pee so I went back to the couch. She finished, flushed and came out and said why not come to bed since it's yours after all. So I got up went to bed and thought we'd just go back to sleep. But honestly I was horny. I always get horny in the morning. So I'm laying there I'm my boxers facing the opposite way and I feel her spoon me and reaches around and grabs my junk again. Annie, I thought you were not into dick. She says it's been 20 years since her last real dick but she's always loved being fucked by strap-ons etc...
So I turn over take off the boxers and start sucking her really really nice big nips. She's liking it and I decided to kiss my way down to her pussy which was smooth as silk. I ate that pussy like I was starved for it. She came like a river. It was quite honestly the sweetest pussy I ever tasted. Eventually I needed to get off so I fucked her silly for about 10 minutes untill I unloaded in her. She said you know I'm not on any kind of birth control do you need to eat your cum out of me. I knew it would not matter but I did as requested anyhow.

I know this has been too long already but long story short, she's spent every night since and we fucked at least twice every day, once before and once after we visit my sister. Sometimes at night or early in the morning we'd fuck again.

We told my sister who was perfectly fine with it. They are still living together but I get to fuck Annie whenever she gets the urge. No my sister doesn't get involved. We never ever have done anything sexual together. But now you can understand why I love my sister. She's the best sister anyone could ask for.