A Thousand and One Night

Needs Tours & Tournaments, and the clean way is to be one of the spouses yourself: arrange a betrothal, host the Grand Wedding, and set your activity Intent to Seduce with your betrothed as the target - the wedding's relationship events can escalate you to soulmates by the ceremony. Higher-grandeur weddings throw more events; Seducer-tree perks tilt the odds. It's not guaranteed per wedding, so budget for a couple of attempts. There were reports around the T&T launch of this not firing when it should; nothing recent confirmed, but if it misbehaves, another wedding is the fix.