Will a person be held accountable for not keeping ties with a brother who was not dutiful to his parents and does not change despite advice?

If your brother is disobedient to his parents and kin, he is in grave danger unless he repents. However, this does not justify cutting him off; maintaining kinship ties is obligatory even with one who severs them, for the Prophet, peace and blessings be upon him, said: "The one who maintains ties of kinship is not the one who reciprocates, but rather the one who, when his relatives cut him off, maintains ties with them." Your brother's misbehavior and transgression do not negate his right to be treated with kindness. Therefore, maintain ties with your brother and continue to advise him gently and wisely, encouraging him to repent.