Eiruvin 6:6-7

Eiruvin 6:6

If five groups of people spent Shabbos together in the same hall, Beis Shammai say that each group must make their own eiruv and Beis Hillel say that one eiruv is sufficient for all of them. Beis Hillel agree that if some of them stay in individual rooms or in an upper level, then each group requires its own eiruv.

Eiruvin 6:7

Brothers, partners who eat at their father’s table but sleep in their own homes, each require their own eiruv. Therefore, if one brother forgot and did not make an eiruv, he should renounce his rights of access in favor of the others. This is only the case when the brothers place their eiruv in one of the other houses in the courtyard; if the eiruv is placed in their father’s house – or if there are no other residents in this courtyard – then they need not make an eiruv at all.