At the time, Jesus’ father (actually step father) was dead. How Mary’s dead husband was going to take of her in her old age would be curious. His other parent, Mary, is the person whom Jesus is seeking to have taken care of. She apparently knew her son had power, as when she asked him to perform a miracle at a wedding feast. There is no indication that Jesus ever put either of his parents down. As for spiritual brothers, I would say his half- or step-brothers (depending on whether you think Mary remained a virgin throughout her life) who were crucified by the Romans would deserve a little credit as also being spiritual brothers. But as for taking care of Jesus’ mother, they’d soon join their father in the grave. John, the beloved disciple, was the only apostle not crucified. He lived to a ripe old age and would have been able to take care of Jesus’ mother. Jesus knew all this. Indeed, Jesus arranged history so as to make all this so.
They were unbelievers/not spiritual brothers and possibly pretty young...