Finn's Baby Brother is the younger brother of Finn Mertens who exists in the Farmworld timeline. Finn saves his parents and little sibling from their burning farmhouse, which was set on fire by the Destiny Gang. In order to protect them, he then sends them away on the family's mule, Bartram. He wasn't born in the standard timeline, as the Mertens family got separated when Finn was an infant.
He doesn't have any clothing or diapers. His skin is a darker peach color, and he has small black dots for eyes. His nose is similar to Magic Man's nose.