I have two five-year-old Jack Russels, from the same litter. One is well behaved, but the other is very poorly behaved. He will pee and poop in the house while I am gone, so I have started crating him whenever I am not home. He also gets into the garbage, even when I am home. We have changed all our trashcans to ones with lids, but he still opens it and gets into it. He rarely listens to commands like sit and come unless there is a treat involved. Why is it he is so poorly behaved and the other is not? What can I do to help him? Or is it just behavioral?
I I had two JTR's for many years--sadly, passed on now. I had a book on JTR's that said they are the "most willful breed," and from my experience this is true. You have two male JRTs who are littermates? This could be the problem. Seems like the 'misbehaver' is jealous and is acting out. Male JRTs can be competitive with each other and perhaps the "bad" one is trying to get your attention --even negative attention. JRT's are like human toddlers in a number of ways.
Can you give a bit more detail? Has the one dog always behaved this way? Do you crate the "good" dog when you leave? Explain your behavior with each dog. Do you spend more time with one than the other? With more information, I may be able to help.