Just as women admire other women without being gay or bi, so do men. Men look towards beautiful men for inspiration in how they want to look themselves, hence male glossy magazines with pictures of impeccably groomed fit looking men provocatively looking at the camera. Men constantly look at other men so they can create there own image and they go to the gym and push weights because they want that tight arse and broad chest they so admire on other guys. This is nothing to do with suppressing there sexuality and all to do with human nature.
http://www.huffingtonpost.com/joe-ko...b_3670740.html
Nick tends to speak his thoughts out loud a lot, I don't see anything gay or bi about him but I do see a lot of honesty and openness that you generally don't see in guys. I can see why Jade and Harry find him attractive. There is a sexuality about him that is intriguing and likely very adventurous.