This video is an Islamic message; it has nothing to do with what Jesus' brothers believed about Jesus. It is full of speculation, assumptions, conjecture and poor inferences. Jesus' brothers saying nothing about Jesus death of the cross doesn't mean they didn't believe it didn't happen for our sin. The video is using silence in the Bible to give their Islamic interpretation. Jude says this Jude, a servant of Jesus Christ and brother of James,

To those who are called, beloved in God the Father and kept for Jesus Christ:

2 May mercy, peace, and love be multiplied to you.

Judgment on False Teachers

3 Beloved, although I was very eager to write to you about our common salvation, I found it necessary to write appealing to you to contend for the faith that was once for all delivered to the saints. 4 For certain people have crept in unnoticed who long ago were designated for this condemnation, ungodly people, who pervert the grace of our God into sensuality and deny our only Master and Lord, Jesus Christ.
Jude
Our common salvation is our Lord Jesus the son of the living God who died for our sin and rose from the dead. Those that reject this message do so at their own eternal peril. Satan will give you a way out of believing the only hope of glory you have such as lying videos like this. Jude considered himself a servant of Jesus His Lord. The brothers of Jesus knew as Mary did that Jesus was and is divine and special beyond all prophets, because of His virgin birth, mission and relationship to God as His word . That made His father God in a unique sense that Muslims, IMHO, deny to their own shame and demise. Deedat who quoted in Arabic "Truth smashes the brains of falsehood" before which debate seems to have had his brains smashed in the end for 9 years before his death. I say learning from the mistakes of others is far better than having to learn from your own, because it may be too late to learn from your own when it comes to matters such as these. I pray that God smashes the brains of the lies against Jesus. May Jesus receive the reward of His suffering!