Jack Dawson was being metaphorical. He isn't royalty of any description, he's a peasant. He isn't even a king of peasants. If I had a dog, and my dog had a child and my dog's child had a pet, that would be Jack Dawson. Lord Voldemort however, is a Dark Lord, which is to say, a warlord with magical powers. Warlords actually rule people, thereby qualifying them for the title of Lord. Furthermore, no I don't know you in real life, you just remind me of someone I used to know.