✅Answer: Please pay attention to the following narration:

1 عَنْ أَبِي خَدِيجَةَ عَنْ أَبِي عَبْدِ اللَّهِ قَالَ: لَا يَرِثُ الْكَافِرُ الْمُسْلِمَ وَ لِلْمُسْلِمِ أَنْ يَرِثَ الْكَافِرَ إِلَّا أَنْ يَكُونَ الْمُسْلِمُ قَدْ أَوْصَى لِلْكَافِرِ بِشَيْ ءٍ.

📚Man la Yahduruhu al-Faqih, Vol. 4, p. 336

Imam Sadiq (peace be upon him) said: 'A disbeliever does not inherit from a Muslim, but a Muslim can inherit from a disbeliever, unless the Muslim bequeaths something to the disbeliever.'

2 عَنْ سَمَاعَةَ عَنْ أَبِي عَبْدِ اللَّهِ قَالَ: سَأَلْتُهُ عَنِ الْمُسْلِمِ هَلْ يَرِثُ الْمُشْرِكَ قَالَ نَعَمْ فَأَمَّا الْمُشْرِكُ فَلَا يَرِثُ الْمُسْلِمَ.

📚Al-Faqih, Vol. 4, p. 335

Sama'ah said: I asked Imam Sadiq (peace be upon him) about a Muslim, does he inherit from a polytheist? He said: 'Yes, but a polytheist does not inherit from a Muslim!'

3 عَنْ عَبْدِ الرَّحْمَنِ بْنِ أَعْيَنَ عَنْ أَبِي عَبْدِ اللَّهِ قَالَ: لَا يَتَوَارَثُ أَهْلُ مِلَّتَيْنِ نَحْنُ نَرِثُهُمْ وَ لَا يَرِثُونَّا إِنَّ اللَّهَ عَزَّ وَ جَلَّ لَمْ يَزِدْنَا بِالْإِسْلَامِ إِلَّا عِزّاً.

📚Al-Faqih, Vol. 4, p. 335

Imam Sadiq (peace be upon him) said: 'People of two different religions do not inherit from each other: we (Muslims) inherit from them (meaning Jews, Christians, and...), but they do not inherit from us, for indeed, Allah, the Mighty and Exalted, has only added to our honor with Islam!'

✅According to the above narrations and others, a Muslim person inherits from a disbeliever, a polytheist, a Jew, a Christian, and a Zoroastrian, but they do not inherit from a Muslim person, therefore, the share of inheritance given by a Christian father to a Muslim child is not a problem and is permissible.

اللَّهُمَّ فَصَلِّ عَلَی مُحَمَّدٍ وَ آلِ مُحَمَّدٍ وَ عَجِّلْ لِوَلِیِّکَ الْفَرَجَ وَ الْعَافِیَةَ وَ النَّصْرَ