Your older sibling made the mistakes so you could watch. That’s a free education with a bruise on it.

Watching somebody else learn the hard way is the cheapest education available. You got the result without the consequence: the argument they had, the class they failed, the person who turned out badly, all of it observed from a safe distance. They paid the fee and you read the notes.

Think of one thing you avoided because you saw it happen to them, and tell them you noticed. Then stop using their record against them, since that is the usual thanks they get. If you are the one going first, the education is still being paid for, and you are allowed to say so.