"Most High" is simply another title of God the Father (Acts 7:48) because we have:
- Heb 7:1 - Melchizedek was king of Salem and "priest of God Most High"
- Mark 5:7, Luke 1:32, 8:28 - Jesus is called "Son of the Most High"
- Luke 1:35 - the Holy Spirit administers the "power of the Most High"
- Acts 16:17 - the apostles called "servants of the Most High"
- Luke 6:35 - Christians are called "children of the Most High"
- Luke 1:76 - John the Baptist called a "prophet of the Most High"
Predictably, the NT title of "Most High" comes from the OT, Dan 4:24, 5:18, 7:25, Deut 32:8, Gen 14:20, Ps 9:2, 46:4, 47:2, 57:2, 77:10, 78:17, 83:18, 91:9, 92:1, Num 24:16, etc, etc.
In his comments on Mark 5:7, Ellicott offers these observations:
(7) Thou Son of the most high God.—This is the first occurrence of the name in the New Testament, and is therefore a fit place for a few words as to its history. As a divine name “the Most High God” belonged to the earliest stage of the patriarchal worship of the one Supreme Deity. Melchizedek appears as the priest of “the Most High God” (Genesis 14:18). It is used by Balaam as the prophet of the wider Semitic monotheism (Numbers 24:16), by Moses in the great psalm of Deuteronomy 32:8. In the Prophets and the Psalms it mingles with the other names of God (Isaiah 14:14; Lamentations 3:35; Daniel 4:17; Daniel 4:24; Daniel 4:32; Daniel 4:34; Daniel 7:18; Daniel 7:22; Daniel 7:25; Psalm 7:17; Psalm 9:2; Psalm 18:13; Psalm 46:4, and elsewhere). In many of these passages it will be seen that it was used where there was some point of contact in fact or feeling with nations which, though acknowledging one Supreme God, were not of the stock of Abraham. The old Hebrew word (Elion) found a ready equivalent in the Greek ὕψιστος (hypsistos), which had already been used by Pindar as a divine name. That word accordingly appeared frequently in the Greek version of the Old Testament, and came into frequent use among Hellenistic or Greek-speaking Jews, occurring, e.g., not less than forty times in the book Ecclesiasticus. It was one of the words which, in later as in earlier times, helped to place the Gentile and the Jew on a common ground. As such, it seems, among other uses, to have been frequently used as a formula of exorcism; and this, perhaps, accounts for its being met with here and in Luke 8:28, Acts 16:17, as coming from the lips of demoniacs. It was the name of God which had most often been sounded in their ears.
Thus, while all Christians are "children/sons of the Most High", Jesus was "The Son of the Most High". This is consistent the New Testament’s repeated idea of Christ being our brother (Heb 2:11-13, 17, Ps 22:22, Isa 8:17, 18, Matt 12:48, 49, John 20:17, Rom 8:29).