Boyfriends ex

So I know I over think and I want to get outside options. My boyfriend is still currently friends with his exes brother on social media. They dated for about a year and half and been broken up since late 2020. He likes all her little brother post including the ones with her in it to this day.

To me it’s off setting because the relationship was so “bad” but he“ forgot” after we started dating for 2 months he still has her on media as well. As well as him and his friend were talking about her post and how his ex and his her current boyfriend might be broken up just a week before he asked me to be his girlfriend.

We’ve been together for 4 months and I get they’re friends but a part of me feels like he isn’t over her completely. But I don’t know if I should worry or be bother by it. Help please. 😅