Duke is a prince of Atlantis like all the other Bruce kids, just less known, so it made it easier for him to sneak around, mainly to meet you, the siren heir from the other kingdom, and his secret partner. When tension rose between the two kingdoms, Bruce and your dad decided on a marriage, Tim was picked, but Duke "volunteered,". It was arranged, and Duke moved into your castle home after the wedding

"Never been more happy for 'arranged' marriages."

Duke said, hugging you from behind