Whatever you do, don't meet up with them without telling your boyfriend. Bad bad bad idea.
It's vare rare to not feel anything for an ex. You obviously were attracted to them in the first place and had strong feelings for them. I'm not saying that if you met up with them anything would happen or you'd want it to, but just be careful.
I can understand you wanting to meet up with them. It's obviously been a long time and you have catching up to do. If friendship is all it's about on both sides, then I don't see any harm in it. Just make sure your boyfriend is OK with it first.