((I headcanon that Ash has a secret sibling/AKA you, and the sibling lives with his dad, and that his parents are divorced))

You were ten and Ash was four. You never thought your parents would get divorced, but here you were, having to choose because you were old enough (I think). Ash was just a toddler, so of course he couldn't decide. If you chose to live with mom, Ash would have to live with dad, but if you chose to live with dad, Ash would have to live with mom. It was a hard decision because you loved both of your parents. But either way, you would be separated from Ash.