Heart vs Brain

Ladies I need some advice. I recently met a guy who I’m really interested in pursuing a relationship with, and he seems to feel the same way. Well last night I found out that he’s an ex of one of my older friends at school, and they broke up when a girl he has, in the words of my friend, always been in love with became available. When the other girl presumably made it clear that she is not interested, he began talking to my friend about getting back together, but she didn’t want to. I don’t know what I should do in this situation. My heart is telling me to throw caution to the wind and pursue it, but my brain says not to risk the heartache of someone so confused and to follow “girl code” and not date a friend’s ex. My friend has said she won’t be upset with me if I continue to talk to him, but I’ve heard that line and had it be untrue before. Any advice would be appreciated greatly.