Why was Dorothy being raised by Auntie Em in the Wizard of Oz?

Other than mentioning at the beginning of the story that Dorothy is an orphan, there is no mention of her immediate family.

Maybe her parents kicked her out because her little dog kept pissing in the house. ~

She’s illegitimate. Her father died of an in-grown toe nail that got infected and went septic. Her mom was Miss Gulch who, when she was born, loaded her into the basket on her bike in the middle of the night and left her on Henry and Em’s doorstep as a storm was approaching. Hence her last name “Gale”.

I thought they had been killed in a previous tornado.

In the books, the fate of Dorothy’s parents is never revealed.

In Wicked, it is said Dorothy’s parents died in a boating accident and she was then adopted by Uncle Henry and Aunt Em