Lahan isn't a random character

Keep in mind how the first half left clues leading up to the attempt on Jinshi's life from very early on. Lahan is another piece of a much larger puzzle and providing information to unravel it.

Lahan is Lakan's nephew who he adopted. He looks similar because they are related.

If anyone is playing Alabama with the family tree it is the emperor and the imperial family whose family tree is a wreath. No really. If you don't mind spoilers look it up.