Since the capital gain has accrued in the hands of sisters, they only have to pay capital gain tax. It is immaterial what they do with the sale proceeds after or before paying capital gain tax. Also, Gift will not be exempt in the hands of brothers.
Because as per section 56 (2)where an individual or a Hindu undivided family receives, in any previous year, from any person or persons on or after the 1st day of October, 2009,—
Clause (a) any sum of money, without consideration, the aggregate value of which exceeds 50000 rupees, the whole of the aggregate value of such sum shal be taxable