The monkeys are still young enough to not have much input yet into what they want to be for halloween. Bro Bro monkey did say he wanted to be a car, but that seemed a little difficult and it doesn't take much to dissaude him. Monkey girl is happy with pretty much anything if it involves dress up especially if it's very girly (ie: princesses, ballerinas, dresses, tutus, etc...). I've been lucky that I've been able to come up with some cute combinations for them up to this point, but it is getting harder and harder lately.
We started when Bro Bro monkey was 1 and he was the scarecrow to his sister's Dorothy. The following year (last year), he was a blue crab (in honor of my Maryland roots) while Monkey girl was Ariel. For this year we were originally thinking of Olivia and either William or Ian, but while Olivia costumes were available, there wasn't much in the way of Olivia's brothers and since I'm not really crafty we postponed that idea. We've since come up with Little Red Riding Hood and little brother is going to be the Baby Big Bad Wolf. He'll be the Baby Big Bad Wolf because for the first time (in a long time) I've found a Big Bad Wolf costume that I thought would be fun to be in while passing out the halloween candy.
Hopefully, we'll be able to continue this costume pairing tradition for a while. I've heard other Mom's talk about how difficult it's been to find their children's preference of costume (and even harder to find it in their size) so I'm grateful that I've learned to do my costume choosing/buying early and online!