I have a 16 week old German Shepherd mix. He is really smart and was quick to pick up potty training. Our house is a split level and we keep a gate at the stairs so Winston doesn't have free range of the house. Recently, when the kids go down stairs and Winston is left upstairs he sits by the gate and pees. I thought at first maybe I had missed a que from him, but I noticed yesterday while we were outside my son left the yard through our gate, told Winston to stay and he sat a peed. Its starting to happen every time he doesn't get to go where the kids are. How do I get him to stop??