The key to understanding this passage is identifying the two persons and one people group being referred to. From the context it is clear that "he that sanctifies" is Jesus. And they "who are sanctified" are all the believers - the whole ecclesia. But who is "the one" from whom both Jesus and all his sanctified followers emanate? There are only three possible fatherhood choices. He is either God, Adam or Abraham.
Many Bibles would have us believe the "one" being referred to is God through the use of capitalization. And it is true that both Jesus and his re-born followers are known as “sons of God.” But clearly it seems more is being emphasized here than just a spiritual connection. A few verses later the emphasis is put upon the fact that we and Jesus share in the same “flesh and blood.” Does that mean the reason Jesus “is not ashamed to call us brethren” is because we are all part of the human family? If so, wouldn’t that argue more for Adam being the “one” who is the father of us all? Fortunately we don’t have to wonder. The answer is provided further down in the text.
It is found in verse 16. "For assuredly he (Jesus) does not give help to angels, but he gives help to the descendants of Abraham."NAS I believe the whole passage reveals that the brethren of Jesus - the sanctified ones referred to earlier - are no less than the descendants/offspring/seed/children of Abraham. Not all his offspring, but only the "children of promise." For we know "they are not all [reckoned] as children [just] because they are Abraham's descendants, but through Isaac your descendants will be named [as true children]" (Rom 9:6). Which is where we learn that God has a chosen people - i.e. a hand-picked chosen nation taken from the seed of Abraham. It will be Isaac, not Ishmael. Jacob, not Esau. Etc.
Now the reason Abraham is routinely rejected by most as the "one" mentioned from whom we all come is because we know that ALL who make up the "sanctified ones" - i.e. the ecclesia" - are not Jewish. Some are non-Jews. The so-called "gentiles." How can they be physical descendants of Abraham (forgetting 5/6 of the nation was scattered among the nations in 722BC)? That's why those teachers who study the Book of Hebrews come to the erroneous conclusion that it was written ONLY to Jewish believers, and not to "gentile" believers as well.
The inescapable conclusion I have reached is that the whole letter is addressed to ALL believers. And therefore ALL believers must be true physical descendants of Abraham. Not just any physical seed, but the chosen spiritual seed, as we read in Galatians 4:28: "But you brethren (addressed to Jewish and non-Jewish believers in Galatia), like Isaac, are children of promise." Being the seed of Abraham doesn't gain us anything, as Ishmael and Esau discovered. You must be chosen "in him [Jesus} before the foundation of the world" (Eph.1:4) to become the "brethren" of the Lord.
I will add one more thought. The reason most opt for Father God being the "one" implied in v. 11 is because they think this verse is trying to convince the reader that Jesus, who is thought to be divinity, could become a true human being. But the only issue being addressed in Hebrews is whether he was an angel or not. Not whether he was divine or not. But post Nicaea, when his divinity was declared a fact by Constantine and included in the creeds, we have been reading this argument back into the text. But it is not there.
"Listen to me, you who pursue righteousness, who seek the Lord: Look to the rock from which you were hewn, and to the quarry from which you were dug. Look to Abraham your father, and to Sarah who gave birth to you in pain; when he was but one I called him, then I blessed him and multiplied him." (Isaiah 51:1,2)