My brother recently converted to Islam, in part because he no longer believes that Jesus was God. If he was, he argues, why did he pray to himself all the time? Why especially in Gethsemane when he was suffering so greatly?
Your brother fails to understand the doctrine of the Trinity. God is one Being who is three Persons: the Father, the Son, and the Holy Spirit. Because these are three distinct persons, it is not unusual for one of the Persons to speak to one of the other Persons. In such a case, as with Christ praying to the Father, he isn’t talking to himself because he is talking to another person.