Hello Again,
We have to go back and see who the audience was when the Apostle Paul was addressing, in context of Romans 8:13
Rom 7:1 Know ye not, brethren, (for I speak to them that know the law,) how that the law hath dominion over a man as long as he liveth?
The Apostle Paul call them brethren:
G80 ἀδελφός adelphos (a-d̮el-fos') n.
1. a brother.
2. (of faith) a brother in our Lord, Jesus.
{literally or figuratively; near or remote; much like G1}
[from G1 (as a connective particle) and delphus “the womb”]
KJV: brother
They were not of the same matrix, they are in the same Lord, Yeshua Hamashia.
God Bless..