I'm 99% confident Real aren't in for Son, this is the first time I've heard it mentioned.
My first suspicion as I've said is that this is Sky Sports making stuff up.
My second suspicion is that this is a PR thing, so Everton can turn round and say "Look, we got a great offer for Richarlison and had to let him go, but we've fought hard and kept hold of Gordon" kind of scenario.
Even if you guys need to raise funds, you're not going to do it by selling a player who just broke through from the academy; it's a PR disaster for the board, and no club is going to pay the obscene money it would take to justify letting him go.