My DF has always been a thief, even as a kid. He was an abusive bastard as a dad too, and we were all terrified of him and carry the lasting legacy of what he did to our self esteem. Sadly, like many kids who had a terrifying parent, all of us still talk to him and feel uneasy about cutting him out of our lives. Guilty almost. Pathetic. But it's how it is.
It's giving me anxiety just to think about doing this, because even though he wouldn't come for me now as an adult, it's like there's a little kid inside who is still paralysed with fear at the thought of provoking him..... but I have found out that he has stolen from one of my siblings. I won't say what as it's very outing... but it's something that would have middling value to him if he sold it, but is priceless to my sibling because of what it represents to them.
Do I take back the item and return it to my sibling, or do I tell my sibling he has the item and let them ask for it back? He will lie about having it. He's stolen from people before and will absolutely brazen it out and make you feel like absolute scum for even suggesting he could be so terrible.