a huge range of very specific terms for familial relations

Yes. A colleague from Nagpur used maamaa the other day in conversation, and realizing that there were some non-Indians in the group he was addressing quickly glossed it by saying "my uncle".

Latin distinguishes between mother's brother avunculus and father's brother patruus. Some other terms in Latin avunculus magnus 'grandmother's brother', avunculus major 'great-grandmother's brother', avunculus maximus 'great-great-grandmother's brother'. Works for aunts, too: matertera 'mother's sister' and amita 'father's sister'.

Ceci n'est pas un seing.