The other day my son was busy playing with his trucks in the family room, when he became very upset at his baby sister because she took one of his trucks, and put it in her mouth.
“That’s MY truck”, he said scolding and ripped it out of her little hands.
My daughter stared at him not understanding, and instead of yelling, she reached again for it, unaware that there was any issue of “mine or yours” at play.