Him or his bestfriend ????

So I was recently dating this guy for abit and we were always on and off he did shit I forgave him, he moved away and we had to end things :// just found out he was dating his ex this whole time ((he has a kid with her but they live In a different state)) and lied to me about it constantly also cheated on me with the same person they cheated on me with the first time, another ex of his that he was dating while dating his other ex! Anyway before all this me and him had a good relationship sort of like he made me happy I loved him I still kind of do, The problem is I'm getting quite close with his bestfriend since he's left and I'm unsure if I should go for him because I feel bad and my ex is suicidal and I'm worried if I do end up going with his bestfriend which happens to be the most kind hearted person that he will commit suicide. Just I don't want to miss my chance on someone because of someone else. But I don't want him to fucking kill himself so I'm stuck