Family Ties (1982)

Season 3: Episode 14

Alex becomes involved with Donna, a young, unwed expectant mother from Elyse's natural-childbirth class but his interest in her becomes an obsession when he starts planning for her child's future and acting as if they were a real family. Donna is flattered by Alex's concern for her and her unborn baby, but soon begins to realize that he is becoming a little bit too helpful.