Movie - A place between a story of Adoption

I'm watching this documentary right now on demand. Its about these two Native American boys (now adults) who were adopted from foster in Canada to an American (CC) family in Redding PA. They were adopted as young boys so they remembered being with the bmom and now one of the boys is making a film about being between both families.I thing that bothers me is the younger brother has basically at 18 yrs old left his adoptive family and went back to Canada to bio family and he hasn't talked to his AP's in 8 years. His issues are growing up without his NA identity and racism he dealt with being NA in a all CC environment. Actually both boys are living in Canada now. The older brother still has a relationship with his AP's.As an AP I would take it as a slap in the face if my kid just left and wouldnt talking to me for 8 yrs. Its like these boys bio mom was an alcoholic who had her kids taken away because she was neglecting them. She said herself she would be drunk for 6 weeks straight and have no idea what day or month it is. Also leaving these babies at home by themselves while she's out partying and they have to change each diapers etc... So you have this family come in and give you a stable home and love and yet because they are CC you just leave?? Im wondering if this something that happens more often with older kids adoption from foster care? Like I said earlier it really annoys me but a great watch anyways.