Relationships (of all sorts) are a big deal in India. Family is even
more IMPORTANT (Bold, All-Caps). It's important to keep all those relationships straight. Hindi has a number of "aa-ee" pairs for various family members, where the "aa" is male and the "ee" is female. (However, "mother" is an "aa" noun.)
First some basics:
Mother, Father: mata, pita (Parents: mata-pita)
Son, Daughter: beta, beti (also lurka, lurki -- actually, officially ladhka, ladhki, but it's pronounced closer to what I wrote first. Also bachcha, bachchi for babies and toddlers, or bachche for children more generally.)
Brother, Sister: bhai, behan
Maternal grandfather, grandmother: nana, nani (Maternal grandparents: nana-nani)
Paternal grandfather, grandmother: dada, dadi (Paternal grandparents: dada-dadi)
Also, baba/babi/babu can be used as a respectful term for a grandparent or elder.
Now the fun begins -- with the aunts and uncles. You've got to keep all those connections straight:
Father's brother and his wife: chacha, chachi (kaka, kaki in Gujarati)
Father's sister and her husband: foofi, foofa
Mother's brother and his wife: mama, mami
Mother's sister and her husband: mausi, mausa
So for our children, who have two "Aunt Chris/Kris" and "Uncle Jim" combinations, it would be totally clear: Mausi Chris and Mausa Jim, and Chacha Jim and Chachi Kris. (Got that?)
Cousins can get just as complicated, as in chachere bhai. Literally, uncle (father's brother) brother, meaning brother through uncle (father's brother) and so forth. (Substitute behan for female cousins.)
The in-laws are equally complex. There are separate terms for husband's elder brother (and his wife), husband's younger brother (and his wife), husband's sister (and her husband), wife's sister (and her husband). Nephews and nieces depend upon whether or not they are children of a brother or a sister.
"Auntie" (spoken as in English) is a respectful term for any older family female friend.
Don't forget that you can append "ji" to any name to show respect.
The combinations seem endless!
And when babies start to babble, just about anything they say is a term for a family member! It's so limiting to have only "mama" and "dada" make sense!