New 10wk old kitten peed and pooped outside box first time ever?

His litter box is in our bathroom and he was in the living room playing with our other cat. I'm not sure he knows the way to the bedroom or bathroom, could this be why?

How long have you had the kitten?

Little kittens have very little control over their bowels and bladders. When they have to go, it's right then. It's probably best to either add a few more litter boxes, or keep her locked in a bedroom with a litter box. When she's a little older she'll have more control.

Are you sure the previous owner litter trained her?

I've had him since Thursday. This is the first time he has done anything outside his litter box, so he was trained.

I suspect he had to go potty and simply didn't know where the litter box was.

I suggest adding an extra litter box or two around the house for a few weeks while he gets acclimated. He is still very young and this will help prevent future accidents. You can remove the extra litter boxes in time.