end of book

So coming to the end of the book which i found to be quite interesting how Steerforth died and it was if he never existed, and here he was the guy who took Emily away but to only resurface dead on a beach. Agnes and David finally being together,,having children and I'm so glad that Copperfield decided to let David find happiness after all that he has been through. Dora dying but yet Im left with in my head,,died from what? Same with Davids mom and brother still,dont know how they died?