Pokémon doesn't usually show parents. This absence makes plenty of sense; the story of Pokémon is meant to be focused on the young trainers and their exploits. Regardless, one can't help but wonder what happened to these important figures in the youths' lives. Ash's father has yet to make a canon appearance and Brock's mother was presumed dead for years in the US. Even in the games, the player seems to only have their mother at home. This is to say nothing of the absolute mystery of Misty's parents.
Misty's mother and father have been virtually absent throughout Pokémon. This doesn't just apply to the anime, either; between the games, the manga, the books and any other form of media, they've made almost no on-screen appearances. Bulbapedia doesn't even have a page about them. However, as sparse as it is, there is information about these mysterious figures. Here's what little is known about Misty's parents.
In the Pokémon anime, neither Misty's mother nor her father has been seen or even mentioned. Her home and her gym are instead watched over by her three older sisters. With the role of guardian fulfilled, Misty's parents don't really need to show up in the anime, so they don't. Meanwhile, in the games, Misty's family isn't mentioned at all. Even her sisters only get a cameo appearance in Pokémon: Let's Go, Pikachu! and Let's Go, Eevee! as trainers at the Cerulean Gym. Besides this, Misty's family remains unseen.
The only known on-screen appearance of Misty's parents in any medium is in the Pokémon Zensho manga, but they're only shown briefly from a distance. Even in this instance, their presence is relatively inconsequential to Misty's life. However, there is one key hint to where they are in Pocket Monsters: The Animation. This book series was written by original series chief writer Takeshi Shudo, and while not canon to the anime, it has several unique plot elements Shudo may have intended for the series but were never finalized.
One of the things mentioned in Pocket Monsters: The Animation is the fate of Misty's parents. Supposedly, they abandoned Misty and her sisters when they couldn't handle the pressure of being Gym Leaders. In the novels, if a Gym Leader lost three times, they would be stripped of their title. While the latter point isn't in the anime at all, the former could still potentially have some truth behind it.
If the anime ever does introduce Misty's parents, it's possible they will take the same route as Brock's mother. Just like Misty's mother, Pocket Monsters: The Animation suggests that she left the family to fend for themselves when she couldn't handle being a Gym Leader. The anime eventually has her come back into Brock's life following a long Pokémon journey, and Misty's parents could easily share this kind of storyline given how long they've been out of the picture.
Whatever their fate, it's clear that Misty's parents aren't an integral part of her life. She's been raised by her sisters and has made plenty of good friends to lead a fulfilling lifestyle. If the fact that she's a Gym Leader at 10 years old isn't proof of this, nothing is. However, if Mom and Dad ever do decide to make an official appearance in the Pokémon anime, it would be a welcome surprise.