Relationship Advice needed

So my ex is one of my best friends. He is a lifelong family friend that I know is always going to be in my life. I don’t have any feelings for him at all anymore. We broke up almost two years ago. My boyfriend gets jealous when him and I hang out and just gets really upset about it. It’s understandable but I feel guilty everytime I hang out with Grant (my ex). I don’t like making Ethan (my boyfriend) upset but Grant is one of my best friends and I know nothing will ever happen between us again. I just don’t want Ethan to get so upset every time Grant and I hang out. Any advice???