Jana337 said:
N/A - father of child's spouse
N/A - mother of child's spouse
Don't they =
tchán - husband's father
tchýně - husband's mother
[...]
tchán - wife's father
tchyně - wife's mother
?
And btw is there any difference in spelling between husband's and wife's mother or it's just a tiny typo (tchýně vs, tchyně), please?
Oh my, it is so complicated in Serbian!

Czech is very economical.
Indeed, I think I'd wind up guessing who's who.

Polish is very much alike Czech in this respect, it's much simpler than in Serbian.

matka (mama) - mother
ojciec (tata) - father
córka - daughter
syn - son
wnuczka - grand-daughter
wnuk - grand-son
brat - brother
siostra - sister
dziadek - grandfather
babka (babcia) - grandmother
ciotka (ciocia) - mother's / father's sister
wuj (wujek) - husband of father's/mother's sister
wuj - mother's brother
ciotka - wife of mother's brother
stryj* - father's brother
stryjenka* - wife of father's brother
*in practice no one uses them nowadys, we use wuj, ciotka respectively
In-lows:
zięć - daughter's husband
szwagier - sister's husband
synowa- son's wife
szwagierka - brother's wife
teść - father of child's spouse
teściowa - mother of child's spouse
teść - husband's father
teściowa - husband's mother
szwagier - husband' s brother
szwagierka - wife of husband's brother
szwagierka - husband' s sister
teść - wife's father
teściowa - wife's mother
szwagier - wife's brother
szwagierka - wife of wife's brother
szwagierka - wife's sister
szwagier - husband of wife's sister
As for teść/teściowa these words are rather formal and the couple usually use tata/mama respectively.