Basic plot:
Two princes are set to inherit their father's kingdom, it would be equally split between them as would any profits that were made. The mother died birthing the younger brother, so the father has held a subconscious grudge against him for his entire life. The father is now on his death bed and upon his death his sons will have control of the kingdom. But the younger brother is jealous of the older one, believing that their father loved him more. One night, the younger brother attacks the older one in a fit rage and during the fight knocks his older brother unconscious. But instead of killing him the younger brother decides to sell him into slavery for profit to fuel his takeover of the entire kingdom. Upon waking, the enslaved older brother has amnesia and doesn't remember who or what he is, but has strange dreams (which are actually just memories) about being someone other than a slave.
Then at this point, there are 2 options: the commoner purchases the enslaved prince or the enslaved prince escapes and runs away from being a subordinate and they meet up. Anything can be mixed with it to add to the plot if desired.
Anyone interested?