Praise be to Allah.
The ultimate fate of your brother rests with Allaah: if He wills, He will punish him, and if He wills, He will forgive him. We cannot say anything definite about his case, but we can speak about the matter in general terms.
With regard to the question of whether the punishment in the grave is continuous or it may stop:
Ibn al-Qayyim said:
The answer is that the punishment in the grave is of two types:
A type which is continuous, apart from what has been narrated in some ahaadeeth which say that it will be reduced during the period between the two blasts of the Trumpet, then when they are raised from their graves, they will say:
“Woe to us! Who has raised us up from our place of sleep.” [Yaa-Seen 36:52 – interpretation of the meaning].
Further evidence that this punishment will be continuous is to be seen in the aayah (interpretation of the meaning):
“The Fire, they are exposed to it, morning and afternoon” [Ghaafir 40:46]
This is also indicated by the hadeeth of Samurah which was narrated by al-Bukhaari, about the dream in which the Prophet (peace and blessings of Allaah be upon him) saw that being done to him (the person who was being punished in the grave) until the Day of Resurrection.
And by the hadeeth of Ibn ‘Abbaas about the story of the two palm branches, where the Prophet (peace and blessings of Allaah be upon him) prayed that the punishment (of the people in the two graves) would be reduced as long as the palm branches did not dry out, so the lessening of the punishment was connected only to the period of time that the branches remained fresh.
And by the hadeeth of Rabee’ ibn Anas from Abu’l-‘Aaliyah from Abu Hurayrah, then he [the Prophet (peace and blessings of Allaah be upon him)] came to some people whose heads were being smashed with rocks, and every time they were smashed, they were then restored, and they would have no respite from that.
And by the story in al-Saheeh of the man who put on two garments and strutted about in an arrogant manner, so Allaah caused the earth to swallow him up, and he will remain sinking down into it until the Day of Resurrection.
And by the hadeeth of al-Baraa’ ibn ‘Aazib about the story of the kaafir for whom a door to Hell will be opened (in his grave) and he will look upon his place in Hell until the Hour comes. This was narrated by Ahmad, and in some versions it was said that that a hole will be made in his grave and he will feel its distress and smoke until the Resurrection.
The second kind: which will last for a while, and then stop.
This is the punishment of some sinners whose sins are not so great; they will be punished in accordance with their sins, then the punishment will be reduced, just as they will be punished in the fire then the punishment will end.
The punishment may be stopped by du’aa’, charity, seeking forgiveness or the reward of Hajj – this may reach the deceased from some of his relatives or others.
(al-Rooh, p. 89)
The last part of this passage answers the second part of your question. We ask Allaah to bestow His mercy upon us. May Allaah bless our Prophet Muhammad.