['My brother recently told me that once, when we were kids, he spit in my orange juice and let me drink it.', "lol that's terrible. Did he do stuff like that a lot back then?", "He kept that a secret for like 15 years so who knows what I'll find out next lol"]
You should prank him to get him back.
My brother recently confessed that one time, when we were kids, he spit in my orange juice.  Apparently he was mad at me for some reason.  He kept the secret for over 15 years.