Headcanon time!

So, in my verse Twiligh Velvet wasn't the first mare of Night Light. He actually dated pretty girl named Mayflower before. Night and May were good friends during high school and everyone just assumed they were an item. And if she really had a crush on the blue stallion, he wasn't so sure about his feelings. They dated for a little while during the college, but then broke up (or more like Night Light broke with her after he realised he didn't really like her that way). Soon enough he met the young writer Twilight Velvet and fell head over hills for her. They quickly became close and then married.

Yep, that means Trixie and Twilight are half-sisters