Conversation so far:
What is known about Eugene O'Neill's family life?
Eugene O'Neill was married to Kathleen Jenkins from October 2, 1909 to 1912, during which time they had one son, Eugene O'Neill, Jr..
How was Eugene O'Neill's married life?
O'Neill's first marriage ended in divorce.
What more is known of Eugene O'Neill's family life besides his marriage to Kathleen Jenkins and son Eugene O'Neill, Jr.?
Eugene O'Neill also had distant relationships with his sons.
How was Eugene O'Neill's marriage to Agnes Boulton?
Eugene O'Neill and Agnes Boulton divorced in 1929, after O'Neill abandoned Boulton and the children for the actress Carlotta Monterey.
Did Eugene O'Neill have any children from his marriage with Agnes?
Eugene O'Neill and Agnes Boulton had two kids, Shane and Oona.
What more is known of Eugene O'Neill's children Shane and Oona besides their mother?
Shane became a heroin addict and committed suicide and Oona married Charlie Chaplin when she was 18 and Chaplin was 54.
Why did Eugene O'Neill disown his daughter?
In 1943, O'Neill disowned his daughter Oona for marrying the English actor, director, and producer Charlie Chaplin when she was 18 and Chaplin was 54. He never saw Oona again.

Question: What happened to the other child?
Self-contained rewrite: What happened to Eugene O'Neill Jr.?