*** This Halacha deals with topic of Yichud. Yichud is the concept that a man may not be secluded with a forbidden woman. Please read all the Halachot on this topic as there are conditions and exclusions that must be fully understood before accepting Lema’ase. ***
There are many complexities to the law of Yichud. Basically, Yichud is the prohibition of a man being secluded with a lady. As explained in the previous Daily Halacha, being alone with a member of the opposite gender is a catalyst that leads to promiscuity and sin.
So the first question obviously raised is whether or not fathers can be alone with their daughters, and if mothers can be alone with their sons. The basic concept of Yichud prohibits a man from being alone with a woman. So can a father be alone with is daughter and not violate this rule? Halacha says it is permissible. It is allowed for a father to be alone with his daughter, and it is allowed for a mother to be alone with her son. Parent and child may even live together, and even on a permanent basis. That’s clearly the opinion of Rav Chida in his Sefer, ‘Yoseph Ometz’.
The Ben Ish Chai writes in his Sefer ‘Od Yoseph Chai’, that the same ruling would apply to grandparents. There is no prohibition against a grandfather being alone with his granddaughter. And there is no prohibition against a grandmother being alone with her grandson. Furthermore, this exception extends to any of the grandfather’s or grandmother’s descendants, be it a grandchild, great-grandchild, great-great-grandchild, etc.
The next question is regarding brothers and sisters. Can a brother and sister be alone? Can they live together? It may come to be that a brother and sister may want to share an apartment and live together. According to Rav Chida it’s clear that it is forbidden for them to have any Yichud whatsoever. Meaning, they may not be alone together and they may not share an apartment together. That is also the opinion of the Ben Ish Chai. However, Chacham Ovadia Yoseph is a little more lenient. He says it is permitted for brother and sister to be secluded so long as they are not together on a permanent basis. A permanent basis is explained as 30 days or more.
Now, there are Poskim that are lenient to allow 2 brothers to live with one sister. They say that the 2 brothers watch each other. It is also permissible for a brother and sister to live together when the mother is also living with them.
So Halacha Lema’ase, there is no Yichud problem with father to daughter, with mother to son, or with grandparents to grandchildren. There is a problem of Yichud with brother to sister, but according to Chacham Ovadia Yoseph they may be secluded and live together so long as it is not for more than 30 days. 2 Brothers may live with a sister, and a brother can live with his sister if the mother is also with them.
