
Some dogs also do this just to mark their territory. Ground them and don't allow the marker free run and nip it in the butt. But u must catch him in the act or he will not know why he is bad. They both may be doing it, one will mark and the other will mark over that. My dogs do it all the time, outside only thankfully.
I know someone that has 2 males one is fixed and the other intack. The intack lifted his leg all the time he was 8 months. They grounded him and sprayed him with water when they caught him lifting and now it's been 3 months with him not lifting in the house. They brought him to my house and he lifted everywhere I kenneled the little bratt. Hopefully now when he comes to visit he is a good boy. :)
Good luck
ttfn :)