Dr. Muzammil Siddiqi, former president of the Islamic Society of North America (ISNA) and member of the Fiqh Council of North America, states that: “A child in such situation should implore Almighty Allah to guide their parents to the path of Islam. This will be their best prayer for them and there is no love greater than that you pray to Allah the Exalted to open their hearts to the truth, bless them in this life, and protect them from the punishment of the hellfire in the Hereafter.
In addition to praying for them, you should also call them to Islam. You can explain to them that Islam is the way of all Prophets and Messengers of Almighty Allah; all true Prophets and Messengers were Muslims, including Jesus, as well as the rest of other Prophets and Messengers (peace be upon them all).
You should also tell them that when they accept Islam they will go back to their original faith because they were born Muslims, but due to outside influences they became Christians. You should also show them the good example of a true Muslim, who treats his parents, be they Muslims or non-Muslims, with kindness and respect.”
Sheikh Hamed Al-Ali, instructor of Islamic Heritage at the Faculty of Education, Kuwait and Imam of Dahiat As-Sabahiyya Mosque, adds: “A lot of du`a’ should be made for your non-Muslim parents so that Allah the Almighty may guide them to Islam. it is advised to choose the best times for du`a’ such as du`a’ when making sujood (prostration) in salah, after the tashahud at the end of salah and before making the salam, in the last third of the night, and between the adhan and iqamah.
It is reported that Abu Hurayrah, may Allah be pleased with him, came to the Prophet (peace and blessings be upon him) requesting him to make du`a’ for his people (the tribe of Aws). So the Prophet (peace and blessings be upon him) prayed: “O Allah, guide the people of Aws to Islam!” So, the People of Aws embraced Islam.
It is also related that the Prophet (peace and blessings be upon him) made du`a’ for Abu Hurayrah’s mother when she was disbeliever, and she accepted Islam by virtue of the du`a’ of the Prophet (peace and blessings be upon him).”