dog urinating now have new pup

Pretend he is a puppy again and give him the same treatment you do the puppy - ie very close supervision, confine him if you can't watch him and make sure he gets super yummy treats and truckloads of praise for going outside.  This is so very very common - dogs often regress in house training if there is a big upheaval in their lives and the new pup is quite an upheaval for him.  He is reiterating to her and everyone else (including himself) that this is most definately "his" home.  Is he neutered?  It may make a difference.  (NB - may.  It's linked to insecurity as well as hormones and happens alot with neutered animals as well as unneutered ones)
 
Make sure you are cleaning up with a biological cleaner or he will still be able to detect traces of the smell.  If there is a spot he favours, try moving his food/water bowls there to discourage him.  If you find any mess, clean it up with him out of sight and don't scold him.  If you catch him in the act, simply take him outside to finish and reward him if he does anything out there.

thankyou so much, this does seem to make sense. yes he is neutered, but was only done 1 and a 1/2 weeks before female pup arrived. i will stock up on his favourite treats and let you know how we get on.

It may take several more months for any hormones to completely leave his system, so if it is linked to hormones be patient and vigilant... he'll get there in the end.

In the meantime, as you wait for the hormones to exit, go back to housetraining 101 and don't leave him unsupervised.  That way, hopefully, the urine-marking won't become habitual.  Some males, even when neutered, don't stop this.  That's why some pet owners neuter before sexual maturity rather than after, despite the sometimes contrary advice they get from various breeders and vets.

Edit...
 
I missed the part where he is neutered.[8D]
 
I would suggest any new change in the household could affect any dog differently.
If he doesn't have a medical problem then stick to your basic house training routine, and praise him to high heaven when he goes outside.
 
I think this will subside once everything gets back to normal....

Since this little one was just recently nuetered, and since the behavior is new, I'd be taking in a urine sample to be checked for a UTI.  These are not at all uncommon after a surgery, and it's always best to check for a medical reason for a change in behavior/habits.