considered brothers. In order for yibbum to apply, all of the following conditions must be met: The brothers share a common father The dead brother had no surviving children, male or female, from any relationship, at the time of his death The brother performing yibbum was born before his brother's death The brother performing yibbum is not forbidden, other than by her marriage to the dead brother, to marry any of his dead brother's widows (e.g. if any of them is his daughter, yibbum does not apply to him at all)(and in the Talmudic discussion of such a case the other wives are referred to as tzarat habat, the "daughter's rival") The brother performing yibbum is physically capable of fathering children The widow is or was physically capable of bearing children Even if some of the brothers do not meet all the conditions to be eligible for yibbum, as long as there is one that does, yibbum applies to him. If there is no brother who meets all of the conditions, neither yibbum nor halitzah applies, except if the widow is forbidden to marry the brother as a result of a prohibition not involving the punishment of kares (spiritual excision), in which case halitzah would apply. Restrictions related to yibbum It is forbidden for any of the widows to remarry until yibbum or halizah has been performed. If the deceased left multiple wives yibbum may only be performed with one of them, at which time the remaining wives are permitted to remarry. Likewise, if yibbum is not performed, halizah is only performed with one of the widows, after which all of them may remarry. If all surviving brothers are still children, the widow must wait until one reaches halachic adulthood, at which time he can perform yibbum or halizah. Similarly, if the brother is missing, the woman is required to wait until he is located. This can lead to a situation similar to an agunah. How yibbum is performed According to biblical law, there is no need for a marriage ceremony between the widow and the deceased's brother as they are already bound by divine decree, thus, they need only cohabit to perform yibbum. Nevertheless, the Sages decreed that the couple perform a marriage-like ceremony called maamar, recite the marriage blessings (sheva brachot) and write a prenuptial agreement (ketubah). Only one brother may perform yibbum. The oldest brother is given