Cal. Welf. & Inst. Code § 306.5

In any case in which a social worker takes a minor into custody pursuant to Section 306, the social worker shall, to the extent that it is practical and appropriate, place the minor together with any siblings or half-siblings who are also detained or include in the report prepared pursuant to Section 319 a statement of his or her continuing efforts to place the siblings together or why those efforts are not appropriate.