Why was John Jarndyce Esther's guardian?

How did John Jarndyce even know Esther existed? We are told when Esther is fourteen, her godmother dies and Kenge appears and reveals that Esther’s godmother was actually her aunt. He asks her if she’s ever heard of a lawsuit called Jarndyce and Jarndyce, which she has not. Kenge says that as part of the lawsuit, Esther will live with Mr. Jarndyce. She will be educated and comfortable, but she must not ever leave the grounds without informing Mr. Jarndyce. What part of the lawsuit is Esther involved in and why is she provided a guardian???