Is Receipt from sale of property, inherited from a relative included/excluded in national income?

No,

Receipt from sale of property, inherited from a relative will not be included in the national income as receipt from the sale of such property is by virtue of transfer of an already existing object.

Explanation:-

The transfer of an existing property is considered just a transfer of ownership from one person to another.

Only the very first sale of an asset is considered as factor income.

Adding the receipt of a second sale of an existing asset will lead to double counting.

Thus it will not be included in the national income.