The people in The Summerhouse are gorgeous - but flawed. They behave like a family but the only thing that binds most of them is love - familial not sexual. That's an unusual bond, between unusual characters who fit nowhere else but with each other.
The story has elements you shoudl baulk at, and all sorts of strange, unexplained, almost supernatural feelings/events. I believed them all. They were so ingrained as part of the character that however implausible it may sound after reading - while I read, I was completely absorbed.
Sometimes ground work is laid by an author in such a messy way, they may have well dug up half the lawn without replanting grass. Willett digs up the lawn, carefully packs as she refills and lays the grass so it looks like the lawn has never been touched. It's a magical trait to have.
So... when drawing characters, if you need to lay ground work, make sure it's so ingrained as part of the character the reader doesn't stumble over it. Don't blurt out what they're like, show me, delicately and sensitively. When you've done that, I the reader, will believe every word you show me.