Sapind has more importance under the Hindu Marriage Act. After marriage, it is a necessary condition not to be connected. In religions, after marriage, the husband and wife are considered to be the same body, so it is a spindle. Defining Sapind, it was decided by the court that it is a relative relationship due to the presence of the body component to the generation below its ancestor. Prohibited under Hindu law and a logical and scientific reason for not allowing marriage in Sapind relationships, according to physiology, marriages in blood-related relatives make children weak and ill.
Socially in India, it is also believed that marriage is not fair in those people where there is mutual reconciliation. Under the present Hindu Marriage Act, the calculation of Sapind determines five (5) from the father and three generations from the mother's side. Sapind relationship is also recognized under the current Hindu law. Marriage to a person of up to five generations on the father's behalf is zero and on the mother's part, it happens for 3 generations.
It has been enacted defining prohibited kinship that the party to the marriage should not be situated in the prohibited relationship. Two persons are said to be under a prohibited relationship -
Brother's or father's or mother's brother's or father's or grandfather's brother's or mother's brother's.
If the brother is the brother's child or sister's child then it will be a prohibited relation.
More detail you can also go with this link - Sapinda Relationship
But if there is a practice in both the parties that allows marriage even in such relations, then they can get married. If such a practice is on only one side, then the marriage cannot take place and the practice should be valid.
According to Hindu scriptures, the Sapind relationship is of utmost importance in 3 works - marriage, succession, and rituals related to birth and death. The family's distance to the parties to the marriage and the successor to the succession is decided by the relationship. The term Sapind is not used in the Hindu Succession Act. The significance of the term is described only in the matrimonial field. Under Hindu law, sapind means a person who has the ability to perform a Pind Daan.