Read Galatians 4:5-7'
4 But when the fullness of the time had come, God sent forth His Son, born[
a] of a woman, born under the law, 5 to redeem those who were under the law, that we might receive the adoption as sons.6 And because you are sons, God has sent forth the Spirit of His Son into your hearts, crying out, [
b]“Abba, Father!” 7 Therefore you are no longer a slave but a son, and if a son, then an heir [
c]of God [
d]through Christ.
The sonship Paul is discussing is contextually speaking about the adoption. And he uses the present tense to describe their position. Beacus YOU ARE sons