26 CFR §1.267(c)-1

1. (a)In general.
   1. (1)The determination of stock ownership for purposes of section 267(b) shall be in accordance with the rules in section 267(c).
   2. (2)For an individual to be considered under section 267(c)(2) as constructively owning the stock of a corporation which is owned, directly or indirectly, by or for members of his family it is not necessary that he own stock in the corporation either directly or indirectly. On the other hand, for an individual to be considered under section 267(c)(3) as owning the stock of a corporation owned either actually, or constructively under section 267(c)(1), by or for his partner, such individual must himself actually own, or constructively own under section 267(c)(1), stock of such corporation.
   3. (3)An individual's constructive ownership, under section 267(c) (2) or (3), of stock owned directly or indirectly by or for a member of his family, or by or for his partner, is not to be considered as actual ownership of such stock, and the individual's constructive ownership of the stock is not to be attributed to another member of his family or to another partner. However, an individual's constructive ownership, under section 267(c)(1), of stock owned directly or indirectly by or for a corporation, partnership, estate, or trust shall be considered as actual ownership of the stock, and the individual's ownership may be attributed to a member of his family or to his partner.
   4. (4)The family of an individual shall include only his brothers and sisters, spouse, ancestors, and lineal descendants. In determining whether any of these relationships exist, full effect shall be given to a legal adoption. The term ancestors includes parents and grandparents, and the term lineal descendants includes children and grandchildren.
2. (b)Examples. The application of section 267(c) may be illustrated by the following examples: