Mistmane is actually a daughter of Celestia who was given up to be raised by her father shortly after her birth. She is unaware of this, as this was during a time when Celestia was not settled enough to have foals (only now in the time of the show would she ever have the ability to settle down) and Equestria’s ties with Neighpon were not very good at the time. Mistmane ended up siring a child with her old friend Sable Spirit shortly before she and the other pillars were sealed away in limbo, and one of that child’s descendants was Night Light, aka Twilight and Shining Armor’s dad.

I am fully aware of the fact that Twilight’s mom is named Twilight Velvet in some merchandise, but I don’t care. Any comments that solely say “But she’s called Twilight Velvet” will be hidden