Talk: Miss Sybil Branson/@comment-96.244.157.57-20121202231001/@comment-4260948-20121224012103

Actually, not true. It could be a "non-dominant" gene, meaning that one of her parents carries the gene for brown eyes, but does NOT have brown eyes herself. As The Crawley Family are blue eyed, it is likely that it came from Mr or Mrs Branson.