Is a relative, whose name was used for tax evasion, entitled to demand money from the sale of properties registered in his name and threaten their owner with reporting him?

Taxes are of two types: permissible and forbidden. Permissible taxes may not be evaded, while forbidden taxes may be evaded.

If the taxes are permissible, then demanding money in exchange for evading them is invalid. However, if the taxes are forbidden, then if a person expends neither money nor effort, they are not entitled to anything. But if they do expend money or effort, then they are to be given compensation commensurate with that.