Addicted Siblings

My sister and I have been a couple for almost 20 years. Growing up, we were pretty much all we had. We were raised by a working single mother, so we spent most of our time alone. When we were horny teenagers, sex between us kind of just happened. We knew it was forbidden, but we just didn't care. It felt natural and sincere, because we truly love each other and have always had. We've obviously kept it a secret (we've only told a mutual, long-time friend about our relationship, and they accepted it, and we only did so because they were suspicious). To keep appearances, we've dated other people on and off over the years, but in our hearts, we belong to each other. The advantage of it, is that it has kept us very open-minded about how we experience sex. I've dated and fucked several women over the years, but my sister is the partner with whom I've experienced the most things.
As we've gotten older, it has gotten harder. I've been able to keep the status of a "desirable bacherlor", casually dating women and staying unmarried. My sister took a different approach, and she married a man. They got married 10 years ago. He's a good guy, she does love him and feels attracted to him. She says sex with him is loving and decent enough, but not as passionate and lustful as it is with me. She loves anal sex, but I'm the only one entitled to fuck her that way (she turns me up to a thousand when she says "I'm your anal whore"). As a married woman, it's a little more difficult for her to make time for us, but it helps that his husband works long hours and travels a lot. It's a good excuse for her to "have lunch" with me every other week. We can spend whole afternoons in hotels.
She's a sex goddess, with the most desirable body I have ever tasted, and the most delicious pair of breasts (check out porn actress Hitomi Tanaka to give you an idea of the kind of body she has). She can fuck me with her pussy for long, pleasurable sessions, or make me cum in her mouth within 10 seconds. Pretty much every inch of her body has tasted my cum, and I've shared her with other men. She loves the taboo of her brother cumming inside of her.
Problem is, she's now pregnant. and it could go either way. She had sex bareback with her husband around the same time she did it with me. She's unsure if it'd be wise to keep the baby. If she decides to do so, I'm determined to support her. Obviously, my role would be limited to being a uncle, but I'd be the best uncle a kid could ever have.