1,313. A Pair of Twins
203:4 If one of a pair of twins died within thirty days, or on the thirtieth day, and the other survived after thirty days, we don't say that since one survived thirty days that the other was necessarily viable. Rather, one does not observe aveilus in such a case.
203:5 If an adult converted to Judaism along with his or her child, these converts do not observe aveilus for one another. This is because a convert is considered like a newborn; they are not legally related to the relatives they had before they converted.