Background
He was sold to the Hutt when he was still quite young, and was brought up as an enforcer, meant to be the muscle backing up the talker.
He fit into this role quite well, and became the favored backup for many of the organization's top enforcers. Including [name], who developed more than just professional attraction to him. They fell in love and plotted to escape the Hutt's employ, preferably killing him in the process.
Their plans never came to fruition, however, as the organization came under assault from a mercenary group. The Hutt and most of his lieutenants were killed, and [wife's name] lost her arm in a battle with her "mother." [Name] found her and managed to get the bleeding stopped.
Having been finally released from the Hutt's servitude, he felt compelled to join with the mercenaries, against the counsel of [wife's name] who wanted to leave, get out of the game, and settle somewhere else. Seeing his insistence on joining, she reluctantly came with him and they were married.
They quickly rose through the ranks and were assigned to the strike group being put together by the Mandalorian, one of their leader's most trusted lieutenants.
Motivation
Conflict: Lifedebt
The mercenary group saved him (and his wife) from the Hutt's permanent employ, and he feels dutybound to work with them until he feels that he has repayed them in full.
Relationship: Lover
While he was still in the "permanent employ" of the Hutt, he fell in love with another enforcer there. After they were freed, they were married, but he felt compelled to join up with the merc group who freed them, and she joined him. She wants out, but he feels that he can't leave them until he has payed off his debt of honor.