Family jewels are important. (Every guy and stepgrandmother will tell you it’s true.)

So it’s fitting that sister act M. Flynn baubles are on the rise. This weekend, Moria and Megan Flynn are adding a big branch to the family tree with M. Flynn Accessories, their first retail shop.

The South End boutique stocks the duo’s twinkling, colorful, and affordable necklaces, earrings, and bracelets, and their preppy-chic handbag line. It will also serve as a showroom for wholesale and bridal clients.

And since the sisters learned to share at a young age, the bright loft houses Hayden-Harnett small accessories, Tocca candles, and Stephanie Johnson cosmetic bags.

Which are so much classier than nutsacks.

M. Flynn Accessories, 40 Waltham Street (617-292-0079 or mflynnstudio.com).