Sisters Katie and Lucy out to show Aussie TV viewers they're not 'blonde bimbos' Big Brother housemates Katie and Lucy Mercer are out to show Aussie TV viewers they're not dumb blondes. Rohan reckons he could turn out to be one of the bad guys on Big Brother Source: Supplied KATIE and Lucy Mercer are out to dispel the "dumb blondes" stereotype when they appear on Big Brother tonight. The Perth sisters enter the Big Brother house as Latecomers, along with Melbourne student Rohan. Katie, 23, a nurse, and Lucy, 21, a student teacher, reckon they are often judged for their looks and not for their brains or personalities. "Some people judge us and we want to show viewers that you can't judge a book by its cover," Katie says. Society thinks of us as blonde bimbos. They don't know who we are or our life experience. There's definitely more to us than meets the eye. I think it will be really fun to show people who we are. That's a big reason why we wanted to go on the show. In a twist, Katie and Lucy will be counted as one housemate. They will enter the house together and if they are eliminated, they will leave together. The vivacious sisters say they are best friends and inseparable. They constantly finish each other's sentences and regularly wear the same clothes. "When Katie goes out to dinner with her boyfriend, I go too," Lucy says. We constantly do everything together. We have a very close bond. We hope to be a means of support (to each other on the show). Rohan is a theatre student who already reckons he could turn out to be one of the bad guys on Big Brother. "There are plenty of people I get along with," he says. It didn't used to be like that but I'm becoming bitter with age. I really need to separate myself before I say something offensive. The sisters' biggest stumbling block could come during the night. "I have been known to sleep talk," Lucy says. That could be an issue. Katie tells me I often sing Twinkle Twinkle Little Star in my sleep. If that happens at 2am it could annoy some of the sleeping housemates. Katie, Lucy and Rohan have all been in lockdown over the past week and haven't seen any of this year's Big Brother.