Baby Daddy Stealer ?

Ok , this girl I use to work with and be somehwhat friends with baby daddy likes me . I told him that's not cool to like me knowing that's his baby momma/ girlfriend and she WAS also my friend ,
He got my number from her phone by the way , he's cute to me and I'm not even gonna like I'm kinda crushing on him but I dont know if I should go any further with him other than texting , what I mean by saying the girl and I was friends before he even texted me she started ignoring me and being mean so technically her and I aren't friends but should I  feel roguish if I date her baby daddy ?