One antisocial kitty/Kitty peeing in sink

I have four cats of varying ages, and the three youngest get along great. However, Milly, my oldest, is rather stand-offish from the rest of the clan. She doesn't play with them, and the only time she'll really acknowledge their existence is when Angel makes her mad and she chases her. (And not in a playful way, more like "I'm gonna beat you up")

Is there anyway I can get her to be part of the group? I feel bad that she's being left out of the group and worry that she's unhappy. Or should I just accept that she's antisocial and hates everyone but my husband?

And instead of making an entire new topic here's my other problem:

One of our cats insists on using the sink and the bathtub as her toilet. She only pees in it, but I'm at a total loss as to what to do. I've only caught her in the act a few times, and I've sternly told her no and moved her to the litterbox but it doesn't seem to help. We keep the bathroom door closed as often as possible but for the sink, all I can think of is keeping a little bit of water in it at all times.

Thanks in advance. :-)

Sometimes a change in peeing behavior can indicate a UTI or other illness. The cat associates pain with the litterbox and avoids it. Please have it checked out.

Some years ago when I had my first Siamese, she started peeing in the sink until I noticed some blood in her urine. She had an infection and I guess this was the only way she had of showing me since I would never have noticed it in the old clay litter.

I'd have her vet-checked just to be certain. Also, if she's not feeling well that could also explain the tension between her and the others.

Vet check for peeing issue is a must. Also you should have atleast 2-3 litter boxes for 4 cats. At least it is in the sink or tub! could be worse!

I feel bad for bumping this, but I kind of forgot about this site until recently lol. I did want to respond to the responses I got though!

I should have mentioned in my first post that both kitties get regular vet check ups and I've mentioned both habits to the vet. The tub and sink peeing has thankfully stopped. Milly, on the other hand, is as vile and hateful to anything that isn't my husband or our roommate as usual. The vet just shrugs and says she's just a mean cat. (Of course this is the poor vet that has been bitten and clawed half to death by her for around 7 years.)