Yes the church at Corinth had some Jews (1Cor 7:18-19). However, the main part of the body where Gentiles (1Cor 6:9-11, 1Cor 8:7, 1Cor 12:2).
So when Paul says brother in his letter to the Corinthian he is referring to both Jew and Gentile believers. Because gentiles are grafted in. Paul labours this point.
----19 So now you Gentiles are no longer strangers and foreigners. You are citizens along with all of God’s holy people. You are members of God’s family.
----17 But some of these branches from Abraham’s tree—some of the people of Israel—have been broken off. And you Gentiles, who were branches from a wild olive tree, have been grafted in. So now you also receive the blessing God has promised Abraham and his children, sharing in the rich nourishment from the root of God’s special olive tree. 18 But you must not brag about being grafted in to replace the branches that were broken off. You are just a branch, not the root.
So when Paul says brothers in 1 Corinthians 10 he is now referring to all Christians Both Jew and gentile.
----10 Moreover, brethren, I would not that ye should be ignorant, how that all our fathers were under the cloud, and all passed through the sea; 2 And were all baptized unto Moses in the cloud and in the sea; 3 And did all eat the same spiritual meat; 4 And did all drink the same spiritual drink: for they drank of that spiritual Rock that followed them: and that Rock was Christ.
Here we see Paul says brothers.. that is to all the Christians in Corinth jew and Gentile alike. There is no ''division'' in scripture Paul is showing it's continuity. from OT to NT
So when Paul says brother in his letter to the Corinthian he is referring to both Jew and Gentile believers. Because gentiles are grafted in. Paul labours this point.
----19 So now you Gentiles are no longer strangers and foreigners. You are citizens along with all of God’s holy people. You are members of God’s family.
----17 But some of these branches from Abraham’s tree—some of the people of Israel—have been broken off. And you Gentiles, who were branches from a wild olive tree, have been grafted in. So now you also receive the blessing God has promised Abraham and his children, sharing in the rich nourishment from the root of God’s special olive tree. 18 But you must not brag about being grafted in to replace the branches that were broken off. You are just a branch, not the root.
So when Paul says brothers in 1 Corinthians 10 he is now referring to all Christians Both Jew and gentile.
----10 Moreover, brethren, I would not that ye should be ignorant, how that all our fathers were under the cloud, and all passed through the sea; 2 And were all baptized unto Moses in the cloud and in the sea; 3 And did all eat the same spiritual meat; 4 And did all drink the same spiritual drink: for they drank of that spiritual Rock that followed them: and that Rock was Christ.
Here we see Paul says brothers.. that is to all the Christians in Corinth jew and Gentile alike. There is no ''division'' in scripture Paul is showing it's continuity. from OT to NT
11And such were SOME of you: but ye are washed, but ye are sanctified, but ye are justified in the name of the Lord Jesus, and by the Spirit of our God.
Yes SOME gentiles were there also .
But When Paul addresses Jews its obvious ( Our fathers ) This is all through Romans ect .