Is it Legal to marry your sister in India? Talking about marrying your sister in India is not legal. It is not permitted to marry your sister in India.
According to Section 5 of the Hindu Marriage Act 1955,
5 Conditions for a Hindu marriage. A marriage may be solemnized between any two Hindus, if the following conditions are fulfilled, namely:
(i) neither party has a spouse living at the time of the marriage;
(ii) at the time of the marriage, neither party
(a) is incapable of giving valid consent to it in consequence of unsoundness of mind; or
(b) though capable of giving valid consent, has been suffering from a mental disorder of such a kind or to such an extent as to be unfit for marriage and the procreation of children; or
(c) has been subject to recurrent attacks of insanity
(iii) the bridegroom has completed the age of 21 and the bride, the age of 18 at the time of the marriage;
(iv) the parties are not within the degrees of prohibited relationship unless the custom or usage governing each of them permits a marriage between the two;
(v) the parties are not sapindas of each other unless the custom or usage governing each of them permits marriage between the two.
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