My 10 year old (full male) has just spent the weekend trying to hump my other 2 year old.( full male)
Older one has never been bred from ,has never had a bitch even so why would he now start this behaviour,?
Any suggestions on how to stop this behaviour welcomed .
Younger one is starting to look haunted lol

Could your younger dog possibly have an infection of some sort ? Sometimes the smell can be like a bitch in heat to an entire dog .

My thoughts to, either infected anal glands, UTI, or a sore/cyst, anything with puss.

Alternatively a close neighbour has a bitch in season, and the Spring is causing the sap to rise so to speak.

MY boys have just spent the weekend with my son's wiem (Bitch) neutered 6/7 years ago,she will try to hump my OH 's leg when he is sitting down,she then
leak's a clear fluid ,(have had soooooo many go's at him ,for him to stop her doing it (he says he doesnt realise she's doing it !!!!!)
Could it be that which is starting this off ?
Younger one did have a bad case of constipation a week or so ago so stopped his chix wings & upped his offal intake seems good now .