It’s inconclusive. I don’t think Shadow Play mentioned anything and I can’t recall anything off the top of my head from the comic that had Cattail in it. Cattail could be either Meadowbrook’s direct descendant or descended from a relative.

Cattail: “I’ve never heard of this Aqua Vine. I don’t know if they ever saw each other again. I do know Mage never had any foals. Her sister was the one who took possession of the notebooks and passed them down, eventually to me.”

Cattail: Oh, I take care of the place. I ain’t much of a cleaner, but from what I hear, my kin wasn’t neither. So I doubt they’d mind a few cobwebs in our ancestral home.

Fluttershy: [gasps] You’re related to Mage Meadowbrook?

Cattail: Mm-hmm.

Fluttershy: Oh, my goodness, Twilight, we did it! Not only did we find Mage Meadowbrook’s old house – we actually found one of her descendants!