Nicola Roberts loves her boyfriend because he is "cheeky and harmless".
She said: "It is serious. He's so cute and he's funny, cheeky, harmless and very polite - he was brought up well.
"What's lovely about him is that he'll talk to anybody; it's nice that I don't have to worry about him. I can go off and dance with the girls."
She believes all of her bandmates - including Cheryl Cole, Kimberley Walsh, Nadine Coyle and Sarah Harding - have a strong Bond and any man that comes into it must deal with that as well as their own relationship.
She told Britain's OK! magazine: "It's not just your life you're letting them into. Us girls are very protective of each other - we're like a solid unit, so you're not just letting the one person into your life, you're letting them into the other four girls' lives too. You have to respect that."