How can we explain the existence of some people who were born Muslims and others who expended a great deal of effort to achieve that?

Firstly:

One of the things concerning which there can be no doubt is that the greatest blessing that Allah bestows upon His slave is to cause him to be born to Muslim parents, to live as a Muslim and to die as a Muslim. This is by the grace of Allah, may He be exalted. This is a blessing from Allah, as the one who is so blessed does not need to seek through different religions to find the true religion that Allah loves and is pleased with, and does not accept any other religion. The individual has not done anything to attain this favour; rather it is pure grace from Allah his Lord, may He be exalted.

But this does not mean that everyone who is born to Muslim parents understands the extent of this blessing and acts in gratitude for it. Rather we see many, many people who are ungrateful for this blessing and do not benefit at all from the fact that from the moment they opened their eyes on this world, they saw Islam and the mosque, and the first thing they heard was the word of Tawheed. Hence these people go astray and follow paths of misguidance and kufr, and they are Muslim in nothing but name, and some of those who are seeking for the true religion may be better than them – although it is not correct to make such comparisons –when they come to know that Islam is the religion of Allah and He does not accept any other religion from His slaves, and they read and ponder until they enter this religion with conviction and adhere strongly to its rulings.

Hence the matter is nothing more than additional grace that Allah, may He be exalted, bestows upon whomever He wills among His slaves that they should be born Muslim. However He does not wrong others, as He has made clear to them the paths of guidance and misguidance, and has shown them His straight path and enjoined them to follow it, and has shown them the ways of the Shaytaan and warned them against following them. And you see some of those who were born to Muslim parents yet they go astray, and you see some of those who were born to kaafir parents following true guidance.

One of the clear examples concerning this matter which will dispel your confusion is what you know about the situation of some of the Messengers and their call and the response to it. We see Nooh (peace be upon him); what did it benefit his son and his wife, when he was the Prophet sent by Allah who called them night and day, but they did not respond and they died in kufr. What did it benefit the father of Ibraaheem (peace be upon him) when his son persisted in calling him, advising him and exhorting him, but he rejected that and even played a role in throwing him into the fire? What did it benefit the wife of Loot, even though she was the wife of a Prophet sent by Allah and he called her to the truth, but she insisted on following kufr? Yet at the same time we see Pharaoh, who was one of the greatest tyrants on earth, yet his wife declared her Islam and disbelieved in her husband. This is how human beings are; either Allah bestows upon some of them the blessing of Islam, and they are grateful for it and strive to adhere to it, and some are deprived of this blessing but they put a great deal of effort into seeking until they arrive at the truth that Allah, may He be exalted, revealed and commanded His slaves to follow His path. And both parties must always say (interpretation of the meaning): “All the praises and thanks be to Allah, Who has guided us to this, never could we have found guidance, were it not that Allah had guided us” [al-A ‘raaf 7:43], and say as the Companions of Muhammad (blessings and peace of Allah be upon him) used to say: By Allah, were it not for Allah, we would not have been guided and we would not have given charity or prayed.

For the one who used to follow a different religion, believing in it and following its Prophet, then Allah, may He be exalted, guided him to the light of Islam and he believed in the Seal of the Prophets, the glad tidings from the Prophet (blessings and peace of Allah be upon him) are sufficient for him:

Al-Bukhaari (3011) and Muslim (154) narrated from Abu Moosa al-Ash‘ari (may Allah be pleased with him) that the Prophet (blessings and peace of Allah be upon him) said:

“There are three who will be given a double reward: a man who had a slave woman whom he taught and taught her well, then he set her free and married her – he will have a double reward; a believer from among the people of the Book who believed (in his Prophet), then he believed in the Prophet (blessings and peace of Allah be upon him) and followed him and believed in him– he will have a double reward; and a slave who fulfils his duty towards Allaah and towards his master – he will have a double reward.”

See also the answer to question no. 11783

Secondly:

With regard to what has happened between you and your parents of differences in culture and religion, this is the same thing that happens among human beings. What has happened to them of divorce is something that happens frequently, especially with repeated problems that create serious friction between them.

What we advise you to do is to focus primarily on telling them about the religion of Islam and calling them to it. If Allah blesses you by guiding them, then there is the strong hope that they may be reconciled, in sha Allah. If it is decreed that they should remain separated, they will have gained the true religion and will be guaranteed salvation from the punishment of Allah.

In fact this is one of the greatest rights that they have over you, that you should make them share this blessing that you enjoy, the blessing of Islam and submission to Allah, the Lord of the Worlds, and worshipping Him alone with no partner or associate. So do not spare any effort in this matter, because it is an important mission, and you will see its good effects, if Allah wills, in this world before the Hereafter. Seek help in that by offering supplication (du‘aa’) for them whilst striving to take practical measures in support of that mission. You can also seek help from experienced people in your city to achieve that. We ask Allah to guide you and help you, and to accept your righteous deeds and guide your parents to that which will bring happiness in this world and in the Hereafter.

And Allah knows best.