Jade and Jordan (Stylistacally, very different. Also brings together images of different generations. They're both girls, but I assumed Jordan was a boy and Jade was a girl when I first heard their names).
Makenna and Megan (Same as Jade and Jordan, but I knew they were both girls).
Necole, Erika and Emielie (This one speaks for it's self).
My ex is named Andrew, and his sister is named Amanda. It's a lovely sibset until you learn that their parents call them Andy and Mandy. ;)
I know a set of sisters named Jennifer and Jenny.
I grew up living with one of my mother's friends for a while. There were 3 kids each, so 6 total. My mother's friend had two sons named William Patrick (Jr.) and Patrick William. Her daughter was named Ashley Marie, and I was Ashley Rose. Yep. It was confusing.
I know three sisters named Brianna, Shyanna, and Dianna. Their mother's name is Anna.
I recently came across someone on facebook whose daughters' middle names were Isabelle, Corabelle, Mirabelle, and Lirabelle. I actually found that to be tasteful as they all had different first names and it tied them together without being tooooo cutesy.