I'm Caucasian and my fiancé is Chinese - I met her on a trip to Tahiti though as chance would have it, it turned out that we actually grew up in adjacent towns in Ohio.
We decided to have a very intimate wedding and only invite our respective immediate family members. We had yet to ever introduce one another to our respective families. We had no extended family and all our grandparents had already passed on, so with each of us having just one sibling, the total number of invites sent out was 4 (one to each set of parents, and one to both my and my fianceé's siblings).
Everyone RSVPed. My sibling said they'd be bringing another guest, as did my fiancée's.
However on the day of the wedding only 6 people turned up and yet everyone we were expecting was at the affair!
Hint 1: The siblings did not bring one another as their +1.
Hint 2: Both my and my fianceé parents are happily married couples and there's no unconventional hanky panky going on between any members of my or my fianceé's family.
Hint 3 (huge hint - possible spoiler... not needed to solve)
Both our siblings are half Chinese, half Caucasian females.