You are definitely over thinking this, it’s not that serious. It could be a range of things from an accidental mis click to him simply condensing his friends list.
If the only updates from you are photos you’ve been tagged in with your family, he may have been constantly seeing photos of random people on his timeline (ie your family) and so unfriended you, especially as you don’t really post much yourself. Not everyone is super interested in your family life.
Someone else could have deleted you like a younger sibling messing around on his phone.
Maybe he forgot it was you if you look different online and he only really knows you by your first name, as it doesn’t sound like you interacted much online. Sometimes I forget who X person online is if I never interact with them, and I just think ‘when did I follow you, Instagram must be playing up’
Whatever it is, it’s that serious in the grand scheme of life. I delete/hide posts from people all the time - it’s just because their content annoys me, not necessarily that I don’t like them as a person. EG people that constantly post long ridiculous rants, constant memes, cringey stuff etc. I have probably met 100s of people that I haven’t added on social media including colleagues, old friends and extended family, and that’s okay.