How they view you and how you view them are not necessarily symetrical. Some of my friends’ kids definitely view me in sort of a familial way, like a favorite uncle, I don’t return that sentiment, but it doesn’t make their view of me any less valid. I’m not giving them any gifts or any more attention than is strictly necessary.
Many of us do view our close friends as a sort of family, I’m much closer to a lot of my friends than I am to some of my family members, it wouldn’t be wrong to say I think of some of them as sort of extra siblings and favorite cousins. I also have relatives I don’t particularly like and try to avoid, but still have to play nice with at family functions, and the kids kind of fall into that category. They’re sort of like the racist uncle, the spoiled cousin, the bitchy new fiance, or the drugged-out family fuck-up. They’re part of the package deal with the rest of the family, but if they just vanished one day I wouldn’t be too broken up about it.