The inside of your home is the den and pack animals naturally like to keep their dens clean. They will want to relieve themselves as far away as possible from where they eat and sleep.
I wouldn't regard it as a problem, per se, he is doing what comes naturally and cleaning up.
Can you install a dog door? If he is having trouble holding on, it could be a urinary tract infection, or just that he needs to be taken out more frequently.
From wolfcountry.net
During nursing the mother will clean the pups and stimulates them to urinate and defecate by licking the genital region. She swallows all of their excretions, keeping the birthing area clean and odor-free.
In wolf packs the entire pack protects the mother and the den and help to raise the puppies.