What should I call my uncle's parents?

You can call them grandparents like your uncle's children. This will be closer.

Equal relatives on the mother's side, when they see how their mother calls them, will follow suit. She, a relative of her elders, is called after her grandfather, daughter and grandmother. For example: mother's uncle, called uncle, mother's aunt, called aunt; Mother's aunt, called grandma, mother's uncle, called grandpa;

Mother's aunt, called aunt grandma, mother's uncle, called aunt grandpa; Mother's uncle, that is, grandpa's brother, is called several grandfathers according to the family ranking. If the relative is the third child, he is called Grandpa Three, the eldest is called Grandpa Big, and the youngest is called Grandpa. The corresponding spouses are called grandmothers.

Extended data:

In family appellation, oral appellation and written appellation have both similarities and differences. Moreover, the face-to-face address of outsiders and each other is different. Although the written, oral, personal and face-to-face titles are different, they are essentially the same in seniority and connotation.

Call relatives during the Spring Festival. Your relatives of the previous generation are generally not chaotic, depending on their relationship with their parents.

Baidu encyclopedia-family appellation