N.Y. Comp. Codes R. & Regs. tit. 18, § 431.10 – Placement in foster family care of children who are siblings.

(a) Foster children who are siblings or half-siblings must not be unnecessarily separated. The social services district is responsible for ensuring that diligent efforts are made to secure a foster family boarding home or agency boarding home which is willing and able to accept the placement of the siblings together, unless placement together is determined to be detrimental to the best interests of the siblings. Such efforts must be documented in the case record in accordance with section 428.6(b)(6), 428.10(d)(6) or 428.11(b)(4) of this Title.
(b) A social services district may make a decision that minor siblings or half-siblings should be separated only if placement together is determined to be contrary to the health, safety or welfare of one or more of the children after consultation with, or an evaluation by, other professional staff, such as a licensed psychologist, psychiatrist, other physician, or certified social worker. Factors to be considered in making a determination of whether siblings or half-siblings should be placed together must include, but are not limited to:
1. (1) the age differentiation of the siblings;
2. (2) the health and developmental differences among the siblings;
3. (3) the emotional relationship of the siblings to each other;
4. (4) the individual services needs;
5. (5) the attachment of the individual siblings to separate families/locations; and
6. (6) the continuity of environment standards pursuant to section 430.11(c) of this Title.
  The factors used by social services districts to determine that siblings or half-siblings should be placed apart must be documented in accordance with section 428.6, 428.10(d)(6) or 428.11(b)(4) of this Title.
(c) If minor siblings or half-siblings are placed apart in foster family boarding homes and/or agency operated boarding homes on an emergency basis, they must be reunited within 30 days unless the social services commissioner or a designated representative determines it is contrary to the best interests of one or more of the siblings to be placed together, after a careful assessment in accordance with subdivision (b) of this section.
(d) Foster parents must be informed if any child placed with them has siblings or half- siblings, and if so, the location of the siblings or half-siblings.
(e) Authorized agencies are responsible for ensuring that diligent efforts are made to facilitate regular biweekly visitation or communication between minor siblings or half-siblings who have been placed apart, unless such contact would be contrary to the health, safety or welfare of one or more of the children, or unless lack of geographic proximity precludes visitation.