Seems like good motivation for some old-fashioned sibling agitation.

"Why does daddy have a tattoo of your name on one arm and Optimus Prime on the other?"

"If you look carefully, your name is under Optimus Prime. Daddy got that one time when he forgot that you're just some kid who turned up on our doorstep one day and never went home. Since you're not really a member of our family, he put Optimus Prime there instead."