You know that he or anyone must receive Christ and reach eternal life through the work on the cross. However, you don't know what happened to him at the end. Christ might have revealed Himself to your brother as he was in a coma at the end - one never knows those things. Let it go.
But Ugly is correct. We don't turn into angels. Thank God for that. After working many years down here, do you think I want to begin a new life ministering to all the people belonging to God as the angels do? I think that we are promised a rest from our works.
If, indeed, your brother found Christ at the end of his life, it would be a good thing. But, if not, in memory of your brother's denial of Christ, lead through intercessory prayer and your testimony as many others to Christ as you can.