I need to check the back story but, Jake and Mia haven't lived with their biological father for years. They have lived with Will, their mother and younger sister. It's an interesting story line because it's something that does happen in RL. It's so tough for everyone in the family, especially the children. When children are bereaved, it has to be least worst outcomes - or "best interests of the child". It means the adults acting like grown ups and putting their own feelings aside to focus on what is truly best for the children.
You're right in saying something's got to give. It usually does when life throws such unexpected shocks and horrors at you.