The Idahan prohibit marriage and sex between members of the nuclear family, with uncles, and with first cousins and their descendants for five generations. Formerly, first cousins who had sexual relations were speared to death, but such relations are now allowed if a payment is made. Polygyny is allowed. A prospective groom's father arranges the details of the betrothal and marriage with the prospective bride's family. His family should pay a betrothal fee, a bride-price, and the expenses of the wedding feast; with the exception of the bride-price (which may be paid much later), these fees are not mandatory. A man without a son may allow a daughter to marry without a bride-price if she and her husband care for him in old age. Residence is patrilocal. Kelabit marriages place a great deal of emphasis on social class; a man need pay a bride-price only when he is of low class and wishes to marry an aristocrat's daughter. There is no firm rule regarding postmarital residence.