Sheikh Sulaymân al-Tuwayjirî
Giving advice is a main principle of our religion. We are obligated to call our relatives and others to follow Islam. Allah says to his Prophet (peace be upon him): “And admonish thy nearest kinsmen” [Sûrah al-Shu`arâ’: 214]
In fact, one the greatest favors we can do for our relatives is to guide them to faith and to enjoin them to what is right and to forbid them from evil and mischief.
Therefore, I would say that you have to try your best to guide your relatives and show them the right path and explain to them the wrong they are doing. It is a good thing for you to encourage them to love Allah’s religion.
You may not abandon them even if your father orders you to do it. This command of his is unlawful. There is no obedience for anyone if it means being disobedient to Allah.
Allah says: "By time! Surely the human being is at loss. Except for those who have faith and do righteous deeds and exhort one another to truth and exhort one another to patience." [Sûrah al-`Asr: 1-3].
This short chapter of the Qur’ân gives a command to enjoin truth and faith to all people, so how could we abandon our closest relations or ignore them?
We are obligated to preserve ties with our relatives. Being kind to relatives is one of the most important Islamic etiquettes. Allah says: “But if they strive to make thee join in worship with Me things of which thou hast no knowledge, obey them not; yet bear them company in this life with justice (and consideration), and follow the way of those who turn to Me: in the end the return of you all is to Me, and I will tell you all that ye did” [Sûrah Luqmân: 15].
In this verse, Allah commands us to treat disbelieving parents kindly and justly. If follows that our responsibility towards our close Muslim relatives will be equal if not greater.
Source: Islam Today