The short answer is:
Pixar has never officially commented on the “Philip Sherman is Nemo’s dad” rumor — likely because they find it too silly to address. But the film’s script, storyboards, and all official materials confirm:
While the address is fictional, it has become a legendary landmark for fans visiting Sydney, often causing tourists to search for a real-life version near Sydney Harbour. Role and Personality Philip Sherman | Disney Wiki | Fandom
He has an eight-year-old niece named Darla , for whom he intends to give Nemo as a birthday present.