I need advice on a sticky situation...?

Ok, My friend is married with her husband for 9 years now, she has 3 kids with another man that she was married to...they've been divorced for over 13 years..her ex-husband of 13 years has been flirting with me and asking me to go out with him..mind you we all work together, he got a hold of my cell number thru another co-worker and he texts me all day long.. the messed up part about it is that I'm feeling him.. he's handsome, older, stable, and veryu attractive and we have a lot in common.. I don't know what to do. My friend and I were good friends and have been for 2 years.. I spoke to him about it and he says that since she didn't raise the kids he has no consideration for her like she didint have for him..(she's a recovering addict) I dont know what to do.. any advice??