And the Bride Wore Plaid by Karen Hawkins (2004, Paperback, Reissue)

This one is an older book of Ms. Hawkins and not her very best, but close enough!
How do you avoid having the family tailsman ring beinging dumped on you by your brother? Leave his weddding early! Unfortunately, Devon St. John finds the ring has been left in his carriage. Someone read his mind. Three of his brothers who had the ring fell into marriage under its spell. His only chance is to find a way to slip it to his younger brother, Marcus, before the ring works its magic. In the meantime Devon feels safe visiting his married friend Malcolm MacDonald, only to find that Malcolm and his wife, Fiona, are having some marital problems. None that can't be fixed because you'll find that Malcolm truly loves his wife. Devon turns in for the evening and is rudely awaken by a young woman who claims that the room he is sleeping in is hers. She is Malcolm's half sister, Kat. Kat normally lives near-by in a cottage where she makes beautiful stained glass and is assisted by seven hulking Scotsmen.....sounds like Snow White! Once in a while she stays at the castle to work on a window and thus "her room." Fiona has a sister, Murien, that she thinks will be perfect for Devon and invites her to stay. She is the opposite of Kat, but Devon's heart is swinging toward Kat because she is more independent and feisty, while Murien charm's tend toward the devious side.
The story moves quickly and is quite enchanting, especially with Kat as the female protagonist. Before it all ends the ring is snatched from Devon and he needs to find it before it is given to his younger brother or the "spell" will be broken. All like a fairy tale in this Regency romance.