Jesus contrasted the present age with the kingdom age. People resurrected to live in the kingdom, sons or products of the resurrection ( Luke 20:36), will not marry (as men do) nor be given in marriage (as women are). They will be immortal, as the angels. [source][source][source]
Like the angels they will also be "sons of God," a common designation for the angels in the Old Testament (cf. Job 1:6; Job 2:1; et al.). This title stresses the God-like characteristic of the angels and the resurrected saints that is in view, namely, their immortality. Even though believers are already sons of God we will become sons of God in a fuller sense through resurrection. Similarly Jesus was always God"s Son in the administrative structure of the Trinity, but He became the Son of God in a fuller sense by resurrection ( Psalm 2:7; Acts 13:33). [source][source][source]
God considers these people worthy to attain to the resurrection of believers because of their faith, not because of any personal merit of their own (cf. Acts 5:41). [source][source][source]
There will be people living in the kingdom who have not yet died and experienced resurrection. Jesus was not speaking about them, only about "sons of the resurrection," namely, those who had died and experienced resurrection (cf. Isaiah 26:19; Daniel 12:2; 1 Corinthians 15:50-57; 1 Thessalonians 4:13-17). [source][source][source]
This explanation was important for Hellenistic readers. The Greeks believed that especially worthy mortals became gods, but this is not what Jesus taught. Rather He said that worthy mortals who are already sons of God will become immortal and incapable of reproducing following their resurrection. [source][source][source]