What should I call my aunt's husband?

My aunt is my grandpa's sister or grandpa's sister, so my aunt's husband can call me grandpa or my grandpa.

In our country, generations come last and birthright comes first. For example, an uncle is his father, his name is uncle, and he is his father's brother or brother. Although there are many differences in seniority and appellation in China culture, the law is obvious. It means the number of generations counted from the closest person. This is the first-level title, which means the number of generations in front of the title and the blood inheritance of the father or mother at the end. The second level, the middle part explains the kinship with the closest person.