Is it okay to date your friend's ex?

Let me start off telling you the back story. I know this guy for a while and I wouldn't consider us "friends" in the beginning, just acquaintances. Anyways we both went to the same school but his girlfriend went to another one. I minded my own business and he did too but there would be days where we would hang out in school (hang out as in just doing homework). His girlfriend was the jealous type and she didn't like the girls that was hanging out with him besides me because she knows I have no intentions for him (and I really didn't). Anyways as years passed me and this guy formed a friendship and his girlfriend was chill about it. Two summers ago I went out of the country and found out they both broke up after a 3 year relationship. I felt bad for the dude because he was so into his girl that he forgot to make some guy friends. Moving on, our senior year we became really close friends. He moved on from his ex and focused on himself. While we were forming this close friendship though he started developing feelings for me and I didn't like that because I know his ex still has feelings for him. Last year in October though I found out they broke up because he found out the girl was cheating on him BUT she told everyone he cheated on her. The guy she hooked up with is actually a friend of mine and he admitted to me that she told him they broke up a long time ago. Anyways I felt bad for the guy and now here we are debating wether on we should date. I knew he was a good guy but I didn't want to jump into a relationship with him right away. His ex was a friend of mine but now knowing what she did kinda got me disappointed. I just don't know if it's still okay to date him or not.