My sister and I are nearly 3 years apart and occasionally we wore the same outfit, or the same but in a different colour. I thought she was pretty cool so was happy to wear what she was wearing.
I can see myself dressing my girls in similar things if I find a bargain and get two of the same! I wont go out of the way to dress them the same though.
As for little people having a 'dress sense', i cant speak for other people's kids, but I know my 20 month old couldnt care less what she is wearing as long as it is comfortable.