All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
First of all, you should know that it is established in the Quran and the Sunnah that only the believers will enter Paradise, and that Allah has forbidden Paradise to those who die as polytheists.
Allah Says (what means): {Indeed, he who associates others with Allah - Allah has forbidden him Paradise, and his refuge is the Fire. And there are not for the wrongdoers any helpers.} [Quran 5:72]
A Muslim cannot intercede for his polytheist relative, even if he is his father, or son, or grandfather, or uncle.
Abu Sa’eed Al-Khudri narrated that the Prophet said: “On the Day of Resurrection, a man will take his father by his hand, wanting to admit him into Paradise [along with him]. However, a caller will call: “A polytheist cannot enter Paradise as Allah has forbidden Paradise for any polytheist. The man would say: “O Lord, O Lord, this is my father; he (the latter) then would turn into an ugly face and a bad smell, and so he leaves him. Abu Sa'eed said: “The Companions of Muhammad consider him to be Ibraheem.”
It means that the one who will intercede for his father is Ibraheem (Abraham) but Allah will not accept his intercession and will transform his father’s face into an ugly form.
This was also mentioned in the Hadeeth narrated by Abu Hurayrah that the Prophet said: “On the Day of Resurrection Abraham will meet his father Azar whose face will be dark and covered with dust. (The Prophet Abraham will say to him): 'Didn't I tell you not to disobey me?' His father will reply: 'Today I will not disobey you.' 'Abraham will say: 'O Lord! You promised me not to disgrace me on the Day of Resurrection; and what will be more disgraceful to me than seeing my father being cursed and dishonored?' Then Allah will say (to him): 'I have forbidden Paradise for the disbelievers." Then he will be addressed, 'O Abraham! Look! What is underneath your feet?' He will look and there he will see a Dhabh (hyena / an animal,) blood-stained, which will be caught by the legs and thrown into Hellfire." So, Allah will turn him into a hyena with abundant fur.
With regard to ‘Abdul-Muttalib, he was the grandfather of the Prophet and he died upon polytheism, the religion of his people who used to worship idols.
Abu Talib, the uncle of the Prophet died upon the religion of his father ‘Abdul-Muttalib. The Prophet did his best and utmost in calling his uncle to Islam and save him from Hellfire, but Abu Talib’s passion for the religion of his parents was stronger than favoring and following the truth, so he died upon polytheism and refused to embrace Islam.
Sa'eed ibn Al-Musayyib narrated from his father, who said: “When the time of the death of Abu Talib approached, Allah's Messenger went to him and found Abu Jahl and `Abdullah ibn Abu Umayyah ibn Al-Mugheerah by his side. Allah's Messenger said to Abu Talib, "O uncle! Say: ‘La Ilaaha Illa Allah’ (None has the right to be worshipped but Allah), a sentence with which I shall be a witness (i.e. argue) for you before Allah. Abu Jahl and `Abdullah ibn Abu Umayyah said, "O Abu Talib! Are you going to denounce the religion of ‘Abdul-Muttalib?" Allah's Messenger kept on inviting Abu Talib to say it (i.e. ‘La Ilaaha Illa Allah’) while they (Abu Jahl and `Abdullah) kept on repeating their statement till Abu Talib said as his last statement that he was upon the religion of `Abdul-Muttalib and refused to say, ‘La Ilaha Illa Allah’. Then Allah's Messenger said, "I will keep on asking Allah's forgiveness for you unless I am forbidden (by Allah) to do so." So Allah revealed (the verse) concerning him {It is not for the Prophet and those who have believed to ask forgiveness for the polytheists, even if they were relatives, after it has become clear to them that they are companions of Hellfire.} [Quran 9:113]
Allah has also revealed about Abu Talib saying to the Prophet (what means) {Indeed, [O Muhammad], you do not guide whom you like, but Allah guides whom He wills. And He is most knowing of the [rightly] guided.} [Quran 28:56]
Al-‘Abbas asked the Prophet saying: “O Messenger of Allah, did you benefit Abu Talib with anything as he used to protect and take care of you, and used to become angry for you?” The Prophet said, “Yes, he is in the shallowest place of Hellfire. Were it not for me, he would have been in the deepest part of Hellfire.” [Al-Bukhari and Muslim]
The narration by Al-Bukhari reads: “He will be in the shallowest place in Hellfire, with fire reaching his ankles and causing his brain to boil.”
For more benefit on the religion of Abu Talib, please refer to Fatwa 91985.
Allah Knows best.