How does Catholic Church explain John 1:31? At John 1:30-31  (NRSVCE) we see John the Baptist introducing Jesus to the crowd:


  "This is he of whom I said, ‘After me comes a man who ranks ahead of me because he was before me.’  I myself did not know him; but I came baptizing with water for this reason, that he might be revealed to Israel."


John's mother Elizabeth was a relative of Mary, mother of Jesus (Lk 1:36) . As such, both John and Jesus would have known each other from childhood. Apparently, John's saying "I myself did not know him.."has a deeper meaning. My question therefore, is: How does the Catholic Church explain the statement of John the Baptist that he did not know Jesus ?
Commenting on John 1:31, St. Thomas Aquinas explains "the statement of John the Baptist that he did not know Jesus" by saying that he


  
  […] precludes an erroneous conjecture from his testimony. For someone might say that John bore witness to Christ because of his affection for him, coming from a special friendship. And so, excluding this, John says, And I did not know him!; for John had lived in the desert from boyhood. And although many miracles happened during the birth of Christ, such as the Magi and the star and so on, they were not known to John: both because he was an infant at the time, and because, after withdrawing to the desert, he had no association with Christ. In the interim between his birth and baptism, Christ did not perform any miracles, but led a life similar to any other person, and his power remained unknown to all.