37 CFR 2.38: Use by predecessor or by related companies.

(a) If the first use of the mark was by a predecessor in title or by a related company (sections 5 and 45 of the Act), and the use inures to the benefit of the applicant, the dates of first use (§§ 2.34(a)(1) (ii) and (iii)) may be asserted with a statement that first use was by the predecessor in title or by the related company, as appropriate.

(b) The Office may require such details concerning the nature of the relationship and such proofs as may be necessary and appropriate for the purpose of showing that the use by related companies inures to the benefit of the applicant and does not affect the validity of the mark.