Are cousins considered family for a sale of property

[Coleen3]

No. See who is considered a related party, below

Sale of Property, Gain or Loss 

You cannot deduct a loss on the sale or trade of property, other than a distribution in complete liquidation of a corporation, if the transaction is directly or indirectly between you and the following related parties.

• Members of your family. This includes only your brothers and sisters, half-brothers and half-sisters, spouse, ancestors (parents, grandparents, etc.), and lineal descendants (children, grandchildren, etc.).
• A partnership in which you directly or indirectly own more than 50% of the capital interest or the profits interest.
• A corporation in which you directly or indirectly own more than 50% in value of the outstanding stock (see Constructive ownership of stock, later).
• A tax-exempt charitable or educational organization directly or indirectly controlled, in any manner or by any method, by you or by a member of your family, whether or not this control is legally enforceable.