Hello Caghe, In our charts the 10th (modernly seen, that is) shows the father and the opposite 4th house our mother.
Our partners, husbands, are shown by our 7th house. So if you want to know about his mother or father, first go to the 7th and then count from there his 10th house (father) or his 4th house (mother).
If you want to know about his sister (your sister-in-law) then go to his 3rd house which is the house where we find peers, ( 3rd of the 7th).
For uncles and aunts I would look at his fathers brothers/sisters, that is: first the 7th house (your husband), then 10th of the 7th (his father) and then count 3 houses from that 10th house to see your father-in-laws brothers/sisters.
For his mother's brothers/sisters, go to your husbands 4th house first (4th of the 10th) and then count 3 houses further.
Starlink