Maglor isn't really Elrond's father, nor is Elrond his son, but both of them forget that, sometimes. especially when Elrond chooses to act like a bratty teenager

"I fear I cannot give you a good answer there." Maglor says. He backs up slightly as she comes forwards, aiming for the harp, and the bundle that Alice can see if she comes closer is a dark-haired child, wrapped in Maglor's cloak, who looks no more than 8 years old. "But I was told that the rulers of this world are fond of jokes and pranks, including rewinding the time of their subjects, and that this might be what happened to me. If this is true, then I apologise, for I must have known you well it seems."