How can one get rid of the effects of the mother's family's envy, which has caused many problems, given the inability to cut ties with them due to kinship and the grandfather's illness?

It is not permissible to accuse anyone of envy without clear proof, and severing ties of kinship is forbidden. This is because the envious person may harbor envy in their absence, and the cure and prevention of envy are not achieved through estrangement. Rather, they are achieved by relying on Allah and seeking refuge in Him, by giving charity and doing good deeds, by extinguishing the fire of the envious person with kindness, by purifying monotheism, and by knowing that Allah alone is the Granter of benefit and harm, as stated in His Almighty قول: {And if Allah should touch you with adversity, there is no remover of it except Him; and if He intends for you good, there is no repeller of His bounty}.