Dividing or classifying the relatives on the basis of nearness or distance of relationship with them is called degree of kinship.
There are three degrees of kinship’s based on the relationship with them :
Primary kin : Those relatives with whom the relationship is very close, direct and near are called primary kin. They can be classified more minutely into primary consanguineous kin or primary affinal kin.
For example: father-son, husband-wife and brother-sister.
Secondary kin : They are primary kin of primary kin. In other words, they are related through primary kin. They are not our primary kin but are the primary kin of our primary kin, hence our secondary kin. For example, father’s brother (chacha), sister’s husband (bahnoi) are secondary kin. The father is my primary kin and his brother is the primary kin of father. Therefore, father’s brother is my secondary kin, the primary kin of primary kin. Similarly, sister is my primary kin but her husband is my secondary kin.
Tertiary kin : They are the secondary kin of our primary kin or primary kin of our secondary kin. Thus, the wife of brother-in- law(sala) called sarhaj in Hindi is tertiary kin because brother-in- law is my secondary kin and his wife is the primary kin of brother-inlaw. Similarly the brother-in-law of my brother is my tertiary kin because the brother is my primary kin and his brother-in-law is the secondary kin of my brother.