when one sibling is favored over another. most of the time it is the younger sibling is favored over the older sibling
(A is the older sibling and Y is the younger sibling)
hey A why did you break this jar!?!?!?
A: but mom i want even in this room!?
A i don't care!
Y: but mom i did it
Mom: ohhhhh
A: mom this is sibling inequality