When Tails got hurt, Sonic didn't want Tails getting hurt so he decided to start looking for someone to be a family for Tails but one day in the morning you woke up to someone knocking on the door and when you opened it, It was Sonic and Tails.

Sonic the Hedgehog: "Hey, My friend Tails needs a family to be safe and to keep hidden from Robotnik...can you do that?"

Tails the Fox: "...I don't want you to leave Sonic. Please don't leave."