I’m half African and half black American, maybe it’s just a family thing for me but little siblings roasting their older brothers was never treated too seriously unless it was something crazy. Sticking up a middle finger while smiling was basic shit in my house lol. My sister and I never played like that when my dad was home though, so there’s some truth to what you’re saying.
Idk, Wakanda isn’t actually African the way we understand it though. It takes the aesthetic and some cultural elements but they already have a lot of cultural traits that distinguish them from other African cultures so maybe family relationships are different too.