§73. Items not deductible; family transactions
In computing net income, no deduction shall in any case be allowed in respect of losses from sales or exchanges of property, directly or indirectly, between members of a family or, except in the case of distributions in liquidation, between an individual and a corporation in which such individual owns, directly or indirectly, more than fifty per centum (50%) of the voting stock.
For the purpose of this Section an individual shall be considered as owning the stock owned, directly or indirectly, by his family; and the family of an individual shall include only his brothers and sisters, whether by whole or half blood, spouse, ancestors, and lineal descendants.