Cat urinating in my sink??

Hi all!  New here.  I have a 2 year old dsh male cat, Sam.  We rescued him and his sister from a shelter about 18 months ago.  They joined my elderly cat, jack, who is 11.  The first year was rough, meaning Jack didn't take too kindly to Sam and Abby invading his territory.  But they have worked things out and sleep together, groom each other, etc.  I keep their cat area--2 cat boxes, 2 water bowls and food, on my master deck and leave the door cracked for them all the time so they come and go. 

So recently, in the last week, Sam has started peeing in my bathroom sink.  He's always loved my sink:  he jumps up and watches me brush, then I let him lick the trickle which he loves, he sometimes sleeps in the sink, he doesn't even mind when I run the water on him a little while he lays in the sink.  But then last week I was brushing my teeth and he jumped in the sink and proceeded to crouch to pee!  I let him finish, just mindful of a dribble mess, but as soon as he was done he jumped down and did a thorough licking.  Then I've caught him a few other times "just about" to go in our sink and I've pulled him off and sent him away--and he does the thorough licking of the genitals again. 

None of my other cats like my sink, but Sam follows me into the bathroom, meows at me when I shower so that when I exit I will turn on the faucet for him.  Does this sound like he could have a bladder infection or is he marking his territory with me? 

Any advice appreciated!

Hi bonbonsaresweet and welcome to TCS!

It's not at all unusual for cats to wee in sinks.  But, since it's a new thing, I've have him checked for a UTI or other issue.

Having said that, my cats weed in the sink, the shower bay, empty litter containers, whatever, until I realised I didn't have enough boxes.. they wouldn't wee where they or any other cat had done a poo.  I have two cats, three boxes and they also wee outside in the garden (I have a large enclosure). With three cats I would have at least four boxes - I know people get away with less, but that's my rule of thumb

But if he hasn't had a trip to the vet in a while, I reckon that's where I'd start.

Has he been seen by the vet?  If not, that would be my recommendation since this is a new habit.  He could have a bladder infection.