Sounds strange, but I rarely photograph families with just girls, most of the families have a sister/brother combo or all brothers. It was one of the easiest sessions that I have done, they played, twirled, hugged, held hands etc. all in one spot! One of the photos that I took from their session won ‘beautiful photo of the week’ and can be found here.
http://www.iheartfaces.com/2015/03/sisters-photo-of-the-week/