what about mr. and mrs. cake? they share a last name, and they're not the apple family, so it's fairly safe to assumn they're married and unrelated. it's more likely that since canterlot is primarily a unicorn city, the band on the horn is an exclusively unicorn tradition, and the other two races have their own traditions for marriage.

But what if

it was a cartoon about talking magical ponies.

well yeah, but it's still interesting to speculate T_T

This is logical.

No he didn't. He met someone at the Gala. She left him a note. He didn't see it. He searched for her.