My b2evolution Version: 2.x

Is there any way to make first and last names mandatory for signing up for the blog? I have only one blog on the site now, and I have some blogs hidden from users unless they are a member. I don't want just anybody and everybody signing up for the member section, basically a way to weed out people I dont want reading the more private stuff. I was wondering if I could make the names mandatory, or maybe someone knows another method I could try.

b2evolution 2.4.7
www.johnhull.org/blog