[Mikey T]

Our younger one, Daisy, is very well behaved and we are feeling bad about the idea of crating both of them when it is only the one misbehaving

If you had a puppy that you were crate training would you then suddenly crate the adult dog as well. Each dog need not be treated exactly the same to be fair. It is acceptable to crate or otherwise confine on dog but not the other.

Any clue on what this guy's issue is and how we can approach the behavior to solve it?

Um you already answered your own question "The problem now is that after spending a good portion of his life at my mothers house he now goes inside sometimes (this was accecptable or tolerated behavior there). "

Training or retraining an adult is no different than training a puppy. An adult with a history of accident can be more difficult to train because you have a large history of unintentional rewarded behavior, but if it is fairly recent change in behavior it general only takes a bit of remedial training to get the dog back on track.


Any clue on what this guy's issue is and how we can approach the behavior to solve it?

 

[Mikey T]

One thing to be concerned about if the accident only occur when your gone is "Seperation Anxiety" With another dog present this is less likely to be the underlying cause but still a possibility that merits attention. Video taping the behavior of the dog while you are gone can be very helpful in ruling in or out seperation anxiety as a cause.

Also you need to rule out medical cause of for the behavior like a UTI. While less common in males they can still get them. It would create urge to go more often, when your home you can let him out when not he simply can not hold out long enough.