I have brought this up before and I know there is no real answer for it - I just can't get my youngster to stop marking.  The two dogs have just had their food and my older dog was sitting near me cleaning herself.  Before I could say a word (I had just turned to read this forum) the youngster cocked his leg near her.  He sees this area as his during the day - he sleeps in his crate at night time in the kitchen and Meg sleeps here in my workroom - her crate under the work top.  I watch him like a hawk during the day and don't let him into the lounge without me - however he still manages a few sprinkles here and there - always something to do with Meg.  When I make a fuss of Meg he really gets frantic for my attention - he just doesn't seem to be a dog who likes sharing me and he seems to be trying to give the message to Meg that everything here is his!!!   I am fed up with cleaning up wee on top of cleaning the dogs after being out for walks.  Sorry just letting off steam - it is impossible to keep him on a lead, crated for the whole day.  He is just so fast.  He has great focus - he learns quickly but this is just so annoying. 

I've a similar problem with my min pin lad. It is definitely scent marking and he's been doing it since he was only a few weeks old. Not all the time but you will see drips on the floor by the kitchen table leg and such places.
I've read about belly bands, but I think they would just be a 'keep the house unsmelly' fix rather than solving the problem. But I might get some so that he can sit with us in an evening and I can relax :)

My youngster started doing it quite early - I felt we had cracked toilet training - I still go out with him into the garden to make sure he has been - and then suddenly he started going again.  As time went on I realised that it was more a message to my other dog then poor toilet training - he just wants to keep telling her that the house is his!  He doesn't challenge her in any other way - she tells him off and is precious of her space - I wonder if that has anything to do with it.  If she was a more easy going dog maybe Eddie could share her space rather than challenge her for it in his own way.  I knew having another dog with Meg and all her neurotic tendencies would be difficult.  I walk them seperately and do lots of training with the youngster on his own.  But I can't change Meg - she will always be what she is.  Hmmm - maybe get another calmer dog - only joking!

Maybe it is just his age and things will improve when he is fully mature and their relationship has settled ?

Oh I do hope so!  I try to remain positive.