1,869. Waiting 90 Days for Yibum/Chalitzah
Yibum v’Chalitzah 1:18
Just as the surviving brother may not perform chalitzah until he reaches adulthood, the same is true of the widow. If a yavam who is a minor engages in intimacy with a yevama who is also a minor*, they should be raised together.
Yibum v’Chalitzah 1:19
As with other women, a yevama may not perform yibum or chalitzah until after 90 days have passed, not including the day her husband died and the day on which she performs yibum or chalitzah. The reason she must wait 90 days to perform chalitzah is because Deuteronomy 25:7-9 says, “If the man doesn’t want to take his sister-in-law... she should remove his shoe” (i.e., equating the two options). Therefore, she is only able to perform chalitzah at a time when she is able to perform yibum. If a brother performs yibum or chalitzah with her during these three months, she fulfills the obligation since she’s not pregnant and no further action is necessary.
*This is not to advocate that such things should be done; the halacha is only discussing the legal ramifications if these circumstances should happen to occur.