What is the ruling on stolen money that has been spent in partnership?

You and your friend are partners in sin for collaborating in the transgression against property. What you took from this money must be returned. If your friend returns the stolen item to his father, then what you took from him becomes his property unless he absolves you. The guarantee (of restitution) is not waived simply because the theft was from the father. If the collaboration and incitement occurred before puberty, then there is no sin upon you, but the guarantee (of restitution) is not lifted.