Really like this one guy

I like this one guy a lot! He’s the kindest sweetest person I may have ever met. He is a family guy, a little nerdy which is so hot to me, and he’s just a good genuine guy. We have a lot in common too.. but

I’m worried there won’t be a spark physically. Is that something that can develop over time?? Which is more important to have and how do you know if there is a spark