Solution

Under Hindu law, a marriage between a man and the widow of his deceased brother (also known as a "levirate marriage") is considered valid, subject to certain conditions. According to Section 5 of the Hindu Marriage Act, 1955, a marriage may be solemnized between two Hindus if the following conditions are fulfilled: (i) neither party has a spouse living at the time of the marriage, (ii) at the time of the marriage, neither party is incapable of giving valid consent to it due to unsoundness of mind, and (iii) the bridegroom is not within the degrees of prohibited relationship unless the custom or usage governing each of them permits of a marriage between the two.   In the case of a levirate marriage, if the marriage satisfies these conditions, it will be considered valid. The Hindu Marriage Act allows such marriages to take place as long as they are permitted by the custom or usage of the parties concerned. Therefore, in the given scenario, the marriage between 'A' and 'B', the widow of his elder brother, would be considered valid if all the conditions are satisfied.