I agree if there were 5 girls and they all had C names it would be pretty lame, but what if its only 2? I don't plan on having the Brady Bunch. I think 2 girls with C names is just right. That way I get my way and then if any more girls should happen to come along we can drop the C thing.
Then the only problem I can see is that maybe the one that gets the non-C name would seem left out