Potty training????!!!!!?

I have a 6 month old male pomeranian/ mini schnouzer mix. When ever we go away, we put him down in the basement. When we come home there is poop and sometimes pee in the basement. The same thing happens if we put him a the creat. I also have another dog.(female) She is a schnouzer and we lets her have free roam of the house if that has anything to do with it. please help. My dad might get rid of him. :(