Is it legislated to remain silent about enjoining good and forbidding evil with relatives if it will lead to a preponderant harm, such as the severing of kinship ties?

If you condemn evil in your heart and do not participate in your relatives' gatherings where evil occurs, then there is no blame upon you. As for condemning evils that you do not witness but know your relatives are committing, then advise and admonish them. If you fear that they will abandon you, then leave the matter to someone else and suffice with condemning it in your heart, for the Messenger of Allah, peace and blessings be upon him, said: "If a sin is committed on earth, whoever witnesses it and dislikes it is like one who was absent from it. And whoever is absent from it and approves of it is like one who witnessed it."