The youngest of the freedom fighters, The Duke was described by Jet as the one "who never had a home", but found one in them. He was best buds with Pipsqueak, and the two were virtually inseparable.
Like Pipsqueak, when Jet went over the line in his quest to stop the Fire Nation, The Duke left and tried to find a new purpose, and found with with Hakoda and his fleet.
During the Day of Black Sun invasion, after it failed to work, The Duke was allowed to leave with Aang and the others, though they had to leave Pipsqueak behind due to his size.
The two were reunited though after the war was over, and they were happy to see each other once again.