So what you're saying is that, Han and Leia sold Rey for some half-portions.
Wow. Han deserved to die.
I don't see how this is any different than literally all alternatives that end up with Rey being left on Jakku by someone who she is screaming at to "come back!"
There's no way Rey is the second child of Han and Leia. For one, they don't exactly seem quiet about the fact that their son Ben is now the second in command of the First Order and murdered a jump of Jedi students, why would they be extremely hush hush about having a second child? And you know C-3PO wouldn't be able to be hush hush about it either. You'd also think Kylo Ren would know of her if she was his sister.
The movie is very deliberate about making sure we never hear any conversation either Han or Leia has about Rey, neither the conversation where Maz asks Han "who's the girl?" or the moment when Han discusses Rey with Leia after meeting her on Takodana (which is referred to later by Leia when Finn says he needs her help to rescue Rey, but never explored otherwise). If
the film itself is going out of its way to keep whatever they're saying about Rey hush-hush, I don't find it very far-fetched to think the characters themselves are likewise doing the same thing deliberately.
This isn't unprecedented in the Star Wars universe; the Empire's downfall came about because Vader had descendants who were hidden for most of their lives until they were old enough to fight the Emperor. If Ben were sent to Luke when he was fairly young (we don't know at what age he left at this point), it's altogether possible - especially judging by Leia's comment that that's when they lost him - that he simply wouldn't have had any contact with his parents around the time that Rey was born; and as he slips to the dark side, it actually becomes paramount that he
doesn't learn about her at all until she's grown.