can a child of age 13 decide to live with an 18 year old sibling if father is unfit?

Question

can a child of age 13 decide to live with an 18 year old sibling if father is unfit?

Answer

What makes an 18-yr-old sibling any better than an "unfit" father? After all, I assume that the same unfit father raised the 18 year old. The bottom line answer is probably No. OTOH, there are a whole lot of missing facts that are needed before any real answer can be given.