“Mazel Tov on your Remarriage!” (But where are the kids?)
There is a minhag (custom) in many Jewish communities found in the sefer Minhagei Vermaiza (The Customs of the Worms Community) that when a parent remarries the children from a previous marriage do not attend the wedding. Poskim differ on the application of this minhag: For example, perhaps it makes a difference whether the parents divorced or they have been widowed. Also, are the children barred only from the chuppah (i.e. the ceremony) or the wedding meal that follows, as well? (It is mentioned in Minhagei Vermaiza that they not attend the meal either, but this is not accepted by all).
There are various explanations given for this minhag, which also impacts its relevance: It may embarrass the kallah (bride) or chosson (groom) to have the children of a previous, failed marriage in attendance. Alternatively, if the children attend a mother’s remarriage, it may seem a betrayal to their father, since once the mother marries another, their father cannot remarry her. Possibly, the children’s presence is a public slight to their father, because the children now must show respect to their new step-father.
All of these possible explanations do not apply if parents are remarrying each other. In such a case, the children may be in attendance, as we find in Chazal regarding Miriam and Aharon who were present at the remarriage of their parents, Amram and Yocheved, after Amram had previously divorced her.