From the Hans Christian Andersen biography "The Life of Hans Christian Andersen. Day By Day", written by DPhil Johan de Mylius:
1828Certificate of Education/Graduation
Gets acquainted with the O'Neill brothers, who he visits during his trip to Portugal in 1866:
"By the way, as luck would have it, a cruel arrow has struck me right in the heart. The little Portuguese is to blame, and I have fallen dreadfully in love with his eyes and the rest of his little person. [It must be the 8 year-old Carlos O'Neill]. The eldest seems a little too serious and silent, but of late I like him far more, as he so kindly approached me and showed me some Italian and Portuguese opera texts; otherwise we did not talk much, for a number of reasons"
(letter to Henriette Wulff dated 14th August).