It's bad to try to separate family members.
Noah's brother is terminally ill and needs someone to take care of his two children, Andrew and Sonia.
Noah wants to help Andrew who he is close with.
Noah decides to adopt Andrew and Sonia and raise them both as best as he can.
Noah decides to adopt Andrew but lets Sonia go into foster care because he does not have strong relationship with her.
Andrew and Sonia both grow up in a stable environment and are able to rely on each other.
Andrew and Sonia are both traumatized from being separated at a young age and grow up troubled.