Unequal attention from in laws

My husbands younger brother had the first grandchild, a boy. He’s only 8 months older than our daughter. The first girl on both sides in 2 generations.

I have noticed a lot of inequality with how they treat him vs her. When they are both in the room and in general. My in laws keep the boy multiple times a week, yet in the last year they have kept her 4 times and never offer.

Has anyone else noticed this with having second or theirs grandchildren? Is this just bc he was the first, am I being sensitive or is it because she’s a girl, or because they prefer him better.

Saddened by it bc she’s amazing, and such a well behaved easy going child.

How would I even address this? husband kind of sees it too