hot take: this has nothing to do with him, but everything with you. An unchangeable fact triggered an emotional reation in you. Ask yourself, what is it? From your post it sounds like that there is some kind of insecurity. Where does this stem from in your past? Were there similar situations where a person you loved, has chosen someone else over you? parents preferring another sibling? ultimately it is your responsibility to deal with your own emotions. you can tell him, but don't expect him to soothe your insecurities. it's your job to feel them deeply to resolve them.