Hey, 60, mwm and I know what you mean about being horny. And I have a wonderful wife who takes good care of me. Some guys are just horndogs is all I can say.
As to your ex-sister-in-law, I'd say go for it man.
Maybe try being a little more romantic than just texting "You wanna fuck?" but you know how you talk to her and how she would respond.
Hope you take that bull by the horns and get into her pants and give her some good old dirty fun too.
Poster to commenter 1 thanks for the words of encouragement man I appreciate it. By the way I'm 60 years old not 46 I don't know how that happened. I totally agree with you that saying let's fuck usually doesn't get you anywhere. I'll probably think of something a little more subtle but it'll probably be just as Direct, I think that's the best way to go with this girl she's no shrinking violet. I hope you know how lucky you are having a woman at home to take out your horniness on. I was married for 32 years and we had an awesome sex life so I'm simply not used to not having daily pussy haha
Let me start with the disclaimer I have never been married, so that makes me especially qualified to contribute to the discussion, for to paraphrase H.L Mencken "The less you know about women, the more likely you are to get married".
Bad idea to approach it in anything like a direct manner. Remember, they are sisters...to accept a move from the man who broke her sister's heart is outside the realm of propriety for many/most women. Don't shit where you (used to) eat. There are plenty of other women you can fantasize about fucking....and even if you get up the nerve, DON'T say "wanna fuck?" or anything like that.