Dragonlord

Your innate magic comes from draconic magic that was mingled with your blood or that of your ancestors. The Dragonlords are people who possess the ability to speak to and tame Dragons, who are their spiritual siblings. It is an innate, hereditary ability passed down from parent to child. Your ancestors probably struck a deal dragons forever ago, or a dragon was indebted to an ancestor of yours. It is unknown how the first Dragonlords gained their powers, or whether Dragons could hatch without them before their creation.

 

Spiritual Siblings

At 1st level, you can speak, read, and write Draconic. Additionally, whenever you make a Charisma check when interacting with dragons, your proficiency bonus is doubled if it applies to the check.

Hatch Dragon

Beginning at the 1st level, you are able to hatch a dragon by naming the dragon and summoning it forth from its egg.

Command Dragons

At the 6th level, you get the command spell if you don't have it already. Dragons have disadvantage when trying to resist the command spell.

Call Dragon

Starting at 14th level, you can call Dragons from up great distances, equal to your level and below. They are forced to come when you call, but they aren't required to do what you ask unless you use the command spell. Your DM can determine whether or not you can choose which dragon you call and the max distance that your call reaches.

Gain Knowledge

Beginning at the 18th level, when you use the command spell on a dragon, you also gain access to their knowledge, magic, and natural might.

For example, you are able to ride a Dragon and command it to share their knowledge of spells. When they share their knowledge about a spell, you gain a page that is one use only of that spell. You can use that spell even if it is above your level. 

When gaining access to their magic, you force them to cast a spell that they know or cast it yourself through them. 

Commanding a dragon and gaining access to their natural might means that you can force the dragon to share their AC and you gain that dragons AC or up to 1 hour (if the dragon has a lower AC than yours then the AC doesn't change).

Your DM can also choose to interrupt access to their knowledge, magic, and natural might in other ways. If your DM allows, what you gain access to is not limited to what has been described here.