Odd dog problem!

[poiuytrewq]

We have two labs, one is 4 and "mine" the other is 3 and O/H's
His is very lively and out on the farm everyday all day, he's home as a pet in the evenings.
Mine is at work on a stable yard with me til lunch time.
They get on very well (they are full brothers but different litters)
I noticed recently that the younger one (farm shut down for Christmas so he's home when I get back) was showing a lot of interest when I got home from work with mine, I put this down to the fact that at my work my dog plays with and sleeps with other dogs which would maybe be an unusual smell on him.
My explination was that on a normal day by the time dog 1 got home dog 2 smelt more familiar and it was less exciting him already being here.
My dog hasn't been to work the past week as there are kids on the yard and he's not a big fan.
However it's increasing, he follows him round constantly and intensely sniffing him.
Tonight I was unsure if he was about to try and hump or pee over mine. (In the house!)
Mentioned to O/H who has also noticed.
Not a massive problem, mine seems oblivious but will be if he does start cocking his leg or trying to hump him.

Any ideas what's going on and why?

 

[Cinnamontoast]

I get a sniff fest if I’ve touched other dogs when I get home. There’s no threat of peeing/humping, but intense paws on my body, extended sniffing. It’s a sign of interest, I don’t let mine progress beyond sniffing. Shove the other dog away, distract if needed with a toy/treat to divert the threat of humping/peeing.

 

[Roxylola]

Sometimes anal glands needing attention can cause this sort of thing. And I have heard of people finding that either the humper or humpee has a bladder infection with this behaviour

 

[PapaverFollis]

I would get anal glands checked and test for a urine infection. My spaniel was definitely more interested in sniffing the sprollie when sprollie had picked up a UTI.