I don't know what it is in novels that make big sisters the good ones, Meg in Little Women, Jane in Pride and Prejudice, Mary in Little House on the Prairie, but they seem to have it pretty accurate, they all (excepting Mary, who I'm pretty sure turns blind) are wise, a good role model, obviously beautiful and feminine,with exquisite manners and dispostion. 
My big sister runs parallel to these, and her recent engagement to her very own John Brooke, or Mr Bingley will no doubt be the fairy tale ending which all these lovely older sisters deservingly acheive. 

(Also, being the second sister, that leaves a respectable, intelligent and poor Professer Baher for me, or, the charming and rather rich and handsome Mr Darcy, I dont mind waiting around for that, or to live in Pemberley.)

Congratulations Milly.


reference: a pretty average article on famous literary sisters.
http://www.guardian.co.uk/books/booksblog/2010/jun/03/sisters-literature-fiction