Recently found a 6 week old male kitten on the street that had been abandoned by its mother (observed him for a few days) so I brought him home and named him Biscuit. Biscuit knows how to use the litter box and he’s weaned off of milk so he can eat wet food and we are currently trying to get him used to dry food. It’s been two weeks now and we have introduced him to my resident cat, 6 year old Kay, using the usually cited technique — a few days of isolation, feeding on opposite sides of a door, then feeding without a barrier — and they can eat around each other fine. I can’t really tell if they’re getting along — Kay does okay when Biscuit is around him chilling, but when he starts running around and trying to snatch Kay’s tail Kay gets understandably annoyed and has swatted at Biscuit a few times (very gently, no hissing, just a warning swat I suppose). Lately, our problem is that Biscuit urinates/defecates outside the litter box (funnily enough, in the same spot where the litter box was when he was first in isolation before we moved him to a separate bedroom from Kay). This has only happened 3 times now but I’m concerned it will become a recurring problem. It has only happened in the area him and Kay mingle in, so I’m thinking this is territorial behavior rather than a medical issue. I’m worried that I’m allowing them to be exposed to each other too soon, or that something else is bothering him. Please help?