In order to understand what is meant by the phrase "the God and Father of our Lord Jesus Christ, " we have to first understand a few basic biblical principles. First of all, God is a Trinity. This means that the single being who is God is expressed in three distinct, simultaneous persons: the Father, the Son, and the Holy Spirit. Jesus is the second person of the Trinity, the Word, who became flesh and dwelt among us (John 1:1, 14). Therefore, Jesus has two distinct natures. He is both God and man. As a man, it was necessary that he be born of a woman and therefore born under the Law (Galatians 4:4). Since he was under the Law, he was obligated to love God and worship Him. It says in Deuteronomy 6:5 that we are to love the Lord our God, and in Deuteronomy 6:13 we are told, "You shall fear only the Lord your God; and you shall worship Him, and swear by His name." So, Jesus had to obey the Law, and he had to worship God the Father. Therefore, we see that Jesus was a man who had to fulfill the law, which included worshiping God. But, because he is also the Son then he is the Son by relation to the Father. Now we can understand why the text would say "the God and Father of our Lord Jesus Christ."
- Romans 15:6, "that with one accord you may with one voice glorify the God and Father of our Lord Jesus Christ."
- 2 Corinthians 1:3, "Blessed be the God and Father of our Lord Jesus Christ, the Father of mercies and God of all comfort."
- Ephesians 1:3, "Blessed be the God and Father of our Lord Jesus Christ, who has blessed us with every spiritual blessing in the heavenly places in Christ."
- 1 Peter 1:3, "Blessed be the God and Father of our Lord Jesus Christ, who according to His great mercy has caused us to be born again to a living hope through the resurrection of Jesus Christ from the dead."
So when we see the phrase "the God and Father of our Lord Jesus Christ," we can now understand that it's speaking of the Trinity and how Jesus, the word in flesh, who was a man required to keep the Law, would have someone he would call God, according to Deuteronomy 6:13, who would be considered the God and Father of Jesus.