The following is an excerpt from The MacArthur New Testament Commentary on John 19.

When Jesus then saw His mother, and the disciple whom He loved standing nearby, He said to His mother, “Woman, behold, your son!” Then He said to the disciple, “Behold, your mother!” From that hour the disciple took her into his own household. (19:26–27)

The only man among the group gathered at the foot of the cross was John himself, the disciple whom Jesus loved (cf. 13:23; 20:2; 21:7, 20 and introduction: “The Authorship of John’s Gospel,” in John 1–11, The MacArthur New Testament Commentary [Chicago: Moody, 2006]). His presence led to an important relationship established by the Lord. When Jesus then saw His mother, and the disciple whom He loved standing nearby, He said to His mother, “Woman, behold, your son!” Then He said to the disciple, “Behold, your mother!” Even as He was dying, bearing man’s sin and God’s wrath, Jesus selflessly cared for those whom He loved (cf. 13:1, 34; 15:9, 13). Evidently His earthly father, Joseph, was already dead. The Lord could not commit Mary into the care of His half brothers, the children of Mary and Joseph, since they were not yet believers (7:5). They did not become believers in Jesus until after His resurrection (Acts 1:14; cf. 1 Cor. 15:7, though the James referenced in that verse may be the apostle James). Therefore He entrusted her to John; he became as a son to her in Jesus’ place, and from that hour he took her into his own household. This may seem a very mundane thing to be concerned about in the hour of His greatest sacrifice, but the beauty of the Savior’s love and compassion for His widowed mother, in the midst of His own excruciating pain, reflects His love for His own (cf. John 13:1).