Jealous kitten?

I am actually posting this for a friend. She has an 8 month old kitten. This guy is a little bit on the wild side. Anyway, he has recently had 2 incidents of peeing outside the box. Both have occurred when others were in the house. (She lives alone). Any ideas as to how to cure this before it becomes habit? We seem to think he is rebelling in response to having guests in the house. A couple of weeks ago it was her son and the grandchildren. But there is also a new man in her life who is becoming a pretty frequent guest.

I was a little short on advice, seeing as we all know I have the 2 most well-behaved cats on the planet.

First find out if she has taken kitty to the vet to check out if it might have a urinary tract infection. Then find out how often she changes the litterbox and if she scrubs it out too. Some cats are persnickity and want a really clean litter box. Then find out if she has changed brands of litter recently. If both of those answers pan out, then I would suggest that kitty is jealous of man friend, and she needs to spend quality play time with kitty alone and see if the man friend will do the same. Or have the gentleman bring over a smelly old raggedy teeshirt unwashed and give it to kitty to lay on, or set it under kitty's food bowl so the kitty can acclimate to the new smell and be more accepting. It just sounds to me like kitty is spoiled and there is nothing wrong with that- as I have several that are as well

Along with everything Hissy suggested, is there a litter box away from all the comotion of new visitors as well?

Thanks guys. Except for the vet issue, all the other things check out ok. I'll tell her the shirt advice, Hissy. I should have known the sweaty shirt solution would pop up somewhere.