I only personally know one baseball situation. The older kid had become a freshman All American and all conference on his way to becoming a first round pick at a ranked program. Junior year his younger brother arrived as a freshman. He was a D1 prospect but nowhere near his brother’s talent. My personal observation was he coattailed his way in on assumptions he was the same player.
After freshman year the kid was farmed out to a JuCo on the premise of returning. After a successful season at a JuCo he wasn’t offered a return. He went onto have a solid career at a mid major.
In softball the second twin received an offer as a package deal with the studdette twin. They were inseparable. It was the only way to lock in the studdette. After two seasons of hardly playing the second twin was released. It could have been she was dumber than a bag of rocks.