Struggles of a fallhard...

So, I am in school and there is a guy, he is 8 years older than me and drop dead gorgeous, funny, sweet, cares about me and makes sure I know I have his support in school... the perfect guy. I would die if I had the chance to call him mine.... But the possibility will never be reality... he is engaged and has a kid.

Now I have no problem dating a guy with a kid but I'm not okay with being a homewrecker. So I am not crossing any lines but he keeps advancing and I'm falling.... I can separate myself sometimes but once we have a conversation again it's just like I was never away.... I'm not going to be a homewrecker nor would I ever allow him to cheat on his fiance. But how do I make it known to him that I care without him thinking I'm trying to ruin his relationship..... I'm struggling