Most English speakers probably just care about You, Mom, Dad, Aunts, Uncles, Cousins, Grandparents, Great-Grandparents and Ancestors, Children, Grandchildren, etc. That's great... as long as you are writing about a monolingual English-speaking family, living in a Anglophone environment or a society that uses the same kind of kinship terms as English does.
Suppose a child is the middle child of five children in a Chinese family. This child has one older brother, one older sister, one younger brother, and one younger sister. The children live with Mom and Dad most of the time. During the holidays, they may visit relatives in the countryside. In the countryside, that's where most of the family is and has been for generations, and there are Grandma and Grandpa (on Dad's side), Dad's brothers and sisters and their spouses and children. In another rural village, there are Grandpa and Grandma (on the Mom's side), Mom's brothers and sisters and their spouses and children. Aside from formal names of each family member, there are also familiar names or terms of address for each family member. The term of address for a particular family member depends on generation level, father's side or mother's side, gender of the person, age of the person relative to the speaker, and age of the person relative to the father or mother (which may include birth order). Realistically, a person will address the target family member by relationship, not by name. So, "Aunt ..." doesn't seem to work here. The translation should be "My father's third younger sister", but the words "father" and "sister" are never used, because in the original language, there is already word that encompasses all of that, and also including the relationship between the target person and the speaker.
Another family is ethnic Korean. This Korean family also has separate addresses for everyone, but in Korean, it takes into account of the gender of the person. If the speaker is male, then his older brother is 형. If the speaker is female, then her older brother is 오빠. "Hiya, older-brother-as-a-female-speaker!" doesn't sound good in English.
How should the writer have the protagonist address all the family members solely by relationship in dialogue and exposition? If it just can't be done, then does it mean one has to anglicize the relationships? For example, in the exposition, the narrator will write everyone's full name, and in dialogue, the narrator calls everyone by name and maybe an English title. So, instead of 姑妈 (for father's older sister), the character just says, "Aunt __________."