In plain words, a person can not marry up to his second cousin from the mother’s side and up to his fourth cousin from the side of the father. It is also necessary the parties should not be apindas of each other from either side.
Hindu Marriage Act
Two persons are said to be within the degrees of prohibited relationships:
if one is a lineal ascendant of the other. For example a Daughter can not marry her father and grandfather. Similarly, a mother can not marry her son or grandson.
If one was the wife or husband of a lineal ascendant or descendant of the other. For example, a son can not marry his stepmother. Similarly, a person can not marry his Daughter-in -Law or son -in-law.
f one was the wife of the brother or of the father’s or mother’s brother or the grandfather’s or grandmother’s brother of the other.
If the two are brother and sister; uncle and niece; Aunt and Nephew or children of brother and sister of two brothers or two sisters. It must have been noticed in some communities the marriage with the wife of the brother and mother’s brother and the first cousins are solemnized, those marriages, in the absence of a custom in the community are not valid marriages.
The parties are not apindas of each other, unless the customs or usage governing each of them permits of a marriage between the two. A apindas relationship with reference to any person extends as far as the third generation (inclusive) in the line of ascent through the mother, and the fifth (inclusive) in the line of ascent through the father.