Future family in laws

Idk but i have this weird thing of wanting to be liked by my fiancé family. We been together 3 years i dont come around as much but i pretty much met everybody and they seemed to like me. But my brother in law has a baby with his gf who hasnt been together as long as us they add her comment on all social media call eachother go out. And i have no relationship with not even his mom yet were still in the awkward hi how are you? Good stage? I just feel they think im young or not wife type i havent had his babys yet cause im in school or maybe its  because im young they think wed have nothing to talk about shes 25 my fiance is but im 20. Idk but thier relationship makes me fel like they dont like somethings about me