四分律行事鈔資持記 2.647

2.647

家界中，初標示，二牒釋。別界不通，即為族攝。同界通家，故是本位。

Regarding the family boundary: first, it indicates and points out; second, it repeats and explains. When separate boundaries do not interconnect, it is subsumed under the clan. A common boundary spans the families; hence it is the original status.