Older Sister Switch Flipped

I'll keep this short and direct: me and my sister are in our 30s. My whole life I knew she was attractive but didn't really feel it the same way. My brain kept a boundary up as best it could and I mostly ignored her and banged my gf.

Recently separated from my wife of over a decade. There was always tension between wife, sister, and mother. Well regardless of any details, wife is gone (ish...nothing is that simple when you have kids) and sister has rapidly warmed up to me. My mother has been very supportive, too. I appreciate it. Truly.

Ahem. Well, not too long ago, I came over to help babysit while she went with BIL on a date. I just caught them heading out for the night, and I don't know what happened...

I like...NOTICED her. It is the first time I've ever looked at my sister (maternal half sibling fwiw) and had legitimate sustained arousal. I always knew she was hot. I never really...felt like she was hot, though.

Fuck me, it's like 3 decades of what the hump have I been missing?! crash landed in my pants. I'd do everything with her right now. She's beautiful and polite and honestly just a great person. How could I not want to fuck her like there's no tomorrow? Ooh this feels new and strange. If it's mutual, even a little, I'd LOVE to kiss her for real just once. She is truly a very pretty woman, but maybe I'm just getting lonely or horny.

Any idea on how to gracefully suggest we break social norms behind a closed door? I trust her to let me down easy if she's grossed out but it. Help plz!