I don't know why I feel like the babies are girls but I do! (maybe because I have two already) anyway, I have a semi short list started. I do want the names to "go well" together but not necessarily match. 
I love having significance with names and both the girls are named after important people in our lives. We will use more family names this time around as well.
DD#1 Cecily Frances
DD#2 Eden Josephine
Here is my list as of now...they can definitely be interchangeable 

Catalina & Evangeline
Maren & Iris
Esme & Iris
Ruby & Esme
Juliet & Scarlet                
 
                
Re: Semi short list :)
Ruby & Esme
Juliet & Scarlet
BFP#1: 11/20/11, EDD 7/25/12, Emily Iris arrived 7/29/12 at 7 lb., 3.5 oz.
BFP#2: 8/25/13, EDD 5/4/14, MMC confirmed on 9/23/13, D&C on 9/26/13
BFP#3: 2/3/14, EDD 10/15/14, fraternal TWINS confirmed 2/21/14, two BOYS confirmed on 4/15/14!
"I love to see a young girl go out and grab the world by the lapels. Life's a bitch. You've got to go out and kick ass." Maya Angelou
~ Auntie to L: 2013 and Peanut: EDD 11/2014 ~
This. I really like Evangeline and Iris together.
And if you really feel they are girls. you might just be right. Within a day or two of my BFP with DD I knew she was a girl. I just had this feeling. She was literally named the first week I was pregnant. My husband says I have uterus ju-ju that makes it so I can make the baby a girl. Haha! We'll see with the next one.
Evangeline maren and juliet. Love the name Eden Josephine too.