Hardwin met and married Iolanthe Peverell of Godric's Hollow. Iolanthe, the granddaughter of Ignotus Peverell, inherited the Cloak of Invisibility, since there were no male heirs in her generation. She told Hardwin that, by tradition in her family, possession of the cloak was kept secret. He respected her wishes, and, from then on, the cloak was passed down to the eldest child of each new generation of the Potter family.
Hardwin may have been the inspiration for the cruel son of a kindly wizard in Beedle the Bard's The Wizard and the Hopping Pot.
- Pottermore (Mentioned only)