Brother and sister and mother

In today's Gospel reading (Matt 12:46-50; also see Mk 3:31-35 and Mk 3:21), the Lord makes this assertion:

'Anyone who does the will of my Father in heaven, he is my brother and sister and mother.'

In the light of objections to Marian devotion (Catholic, Orthodox or otherwise), it becomes generally necessary to discuss the topic of our Lord's "brothers" (considering assertions of our Lady's perpetual virginity) and our Lady's state of grace or sinlessness.

But my son Justin, seven years of age, homed in on what was really important: "What is the will of our Father in heaven?"

What came to mind was the Father's command at our Lord's transfiguration (Lk 9:35):

'This is my Son, my Chosen; listen to him!'