Is it permissible for the family of the victim to accept blood money in exchange for pardoning the intentional killer?

It is permissible to accept blood money from a deliberate killer in exchange for waiving the right to retribution (Qisas), based on the Almighty's saying: "So whoever is pardoned anything by his brother, then pursuit [of payment] should be with good conduct and payment to him with excellence," and based on the Prophet's (peace be upon him) saying: "Whoever has a person killed belonging to him, then he has the choice of two best options: either blood money is paid, or retribution is carried out."