Notions of who is and isn't part of your family or lineage can be wildly, wildly different from modern Western ideas that the family is primarily a genetic relationship. Things like, your mother's sister's sons are part of your family, but your mother's sister's daughters are part of her husban's family and not part of your family.
It actually caused the great rift that forced Anthropology to drag it's head out of it's imperialistic ass. This guy named Chagnon was bribing Yanomami people in the Amazon to tell him who their genetic relatives were. This was a big taboo (and they almost certainly lied to him) which raised massive ethical issues. And on top of that, what he was trading were shotguns and machetes. The introduction of lots of weapons may have screwed up the balance of power in the region badly and set off a lot of very destruction wars, getting many people killed.
Well, it set off a war in western anthropology between Chagnon supporters and people who were horrified by his unethical behavior and by the destruction it probably caused. It lead to a pretty vicious internal debate that lasted for decades and ultimately resulted in both anti-imperialist anthropology and the formation of modern ethical standards in anthropology. In some ways the debate is ongoing, as the question of whether anthropologists are in any way helping our subjects, or merely preying on them, is being discussed. There's a thread with some merit that says western anthropologists should stop as we can only be parasitic outsiders and the knowledge we produce often harms and rarely helps our subjects and partners. From there the question of how we can transform anthropology in to something that is useful and helpful to the people we study has emerged.
This was one of the reasons I personally abandoned the notion of professional anthropology, because well I found that the most useful form of it was to study western culture, and the most accurate critics were nearly always some flavor of Marxists. The issue is the only way to make any money is to exploit Native groups or literally work for the State department. Or fight the administration in a continually losing battle for funding. None of which particularly interested me.
It's a valid and valuable question and for my part I actually regret grouping genetic with familial in my wording as a social family can be just as or more important than genetic family, something any of us but particularly those of us with shitty genetic family members can relate to.
That being said I think anthropology as a field can be as valuable as it can be ethical, so essentially the information from it can only be valuable if it comes from no contact or unintrusive contact. I think the toughest question is how to make that contact unintrusive though.