The Parents whole deal..
(Spoilers, obvs)
Why did they need to commit suicide? It's not like Brahms was going to follow them to wherever they went.
I honestly thought Malcolm and Greta would adopt the Brahms doll and it would turn out that the doll was ageless and had had many parents before the original pair. Any visitor the doll would take a shining to would become possessed by it and forced to take care of it as if it were a real child. A much better plot in my opinion. The doll took a shining to Greta, set her up with Malcolm and forced the old parents to leave them everything and kill themselves.
Also, when Greta's friend is on the phone and predicting what she's doing "I bet you're wearing the orange dress, having a glass of wine" etc. Was that supposed to be Brahms?