Everyone in the future according to Roddenberry is bisexual.
Vulcan betrothals are "economic" or "status" transactions by the family heads.
Planning the shape of their families "finances" and the destiny of it's bloodlines, it's more than possible that "gay" marriages would be arranged on purpose so that land or ships can change hands, without having to worry about second generation losses from unproductive or inadequate progeny, where the "families" decide that they only want their intermingling to last a single generation since (cloning, I know.) it's difficult for like sexes to conceive.
So there's every chance that you're a seven old Vulcan and it's betrothal time, but the person waiting to join with you mentally is exactly the same gender as you are because the political union is more important than the production of children with shared lineage and the consolidation of familial power.