Lemme establish something first: Rosemary, Thyme, Sage, and Parsley are all my OCs! Unless Disney THEMSELVES say otherwise, these four characters are completely fanmade.
In my AU, Rosemary is the eldest of the entire family, though Oswald treats her like a little sister. When things get serious, THAT’S when he’ll start listening to her.
Thyme had been around since the 1940s, and had befriended the Gremlins. That’s how she’s closest with Prescott. She envys her siblings for being more popular than her, but just like an anime tsundere, she still loves them though she won’t say that out loud because of her pride.
Sage and Parsley are relatively new. They are both crippled because the Shadow blot actually harmed them in the Thinner Disaster. Parsley is paralyzed from the waste down and Sage had a part of his ear melted off.
Their ages go like this:
Rosemary: 93 (1924)
Oswald: 90 (1927)
Mickey: 89 (1928)
Thyme: 71 (1946)
Sage: 45 (1972)
Parsley: 20 (1997)