Congratulations, my friend! The names that are popular in your country will likely give your sisters an edge when it comes to popularity, so i sugest the girls names that are the most popular in your country :)
You can easily goodle this. For instance "top 10 girls names in USA"
There are lists and lists of girl names online just type baby girl names into google. Personally, I think it would be a cool concept to name them both with the same first letter in their names being twins for example, Natalie and Nicole or Jennifer and Jessica, Ashley and Amy. I think thats a cool concept and I'd name them like that. Cheers on the twins! And best of luck to you and your mom!
Whatever you decide to name them make sure they dont rhyme or sound similar... that is really tacky. Twins might look just alike but they are two separate people with two separate identities. Take your time and go through baby name books or something and come up with unique individual names. Find names that have meanings to them.
NoRHYMING NAMES PLEASE! Give them their own identity! If a family name sounds pretty or 'smart'---- then pic a middle name from each side of the families! I have a niece named Jill Copeland! On the other side of the family, the name Peace( as in Peace College in N.C. ) Also think about the meanings of the names. we could not use that name because our last name is LILLY! but our next generation could name a girl LILLY(spelled the same way) --- but not Peace Lilly). lol lol