I've named changed for this as will out me with dps sis.
try to keep it short last year I found a receipt for a sex toy and asked DP about it (assumed it was a present for me!) after first saying that he’d bought it for a male friend for a joke he eventually admitted he’s bought it for a female friend of his sisters who he’s known for years, he said at a party his sister had it came up that this woman had never had one and he bought her one because he thought it would be funny. I was annoyed that he’d buy something so intimate for another woman but he convinced me that it was just a joke and that there was nothing to worry about.
This weekend his sister was over and I mentioned it assuming she was in on the ‘joke’ and she didn’t know what I was talking about, said she didn’t remember the conversation and told DP it was weird
now I feel like a fool for being convinced this is ok. I have no other reason to be suspicious and am sure nothing is going on between them but I can’t get how he thought it was ok or her actually as she accepted it and knows its from him