“And he answered and said unto them, My mother and my brethren are these which hear the word of God, and do it.”
Luke 8:21 — Greek Interlinear
Church Fathers on Luke 8:21
Our Lord had left His kinsfolk according to the flesh, and was occupied in His Father’s teaching. But when they began to feel His absence, they came to Him, as it is said, Then came to him his mother and his brethren. When you hear of our Lord’s brethren you must include also the notions of piety and grace. For no one in regard of His divine nature is the brother of the Savior, (for He is the Only-begotten,) but He has, by the grace of piety, made us partakers in His flesh…
But those who are said to be our Lord’s brethren according to the flesh, you must not imagine to be the children of the blessed Mary, the mother of God, as Helvidius thinks, nor the children of Joseph by another wife, as some say, but rather believe to be their kinsfolk.
Think what it was, when the whole people stood by, and were hanging upon His mouth, (for His teaching had already begun,) to withdraw Him away from them. Our Lord accordingly answers as it were rebuking them, as it follows, And he answered and said to them, My mother and my brethren are they which hear the word of God, and do it, &c.