I have a phpBB Forum and before i add a wordpress blog to the site, i want to know if it is possible to have them so that, when someone signs up to my forum, that same membership works for the blog too (or vise versa).

Rather than a member needing to create another membership for the other one.
Can anybody let me me & maybe tell me how to do it please?
Note: add the blog myself no problem, its just the making one membership for both im asking about.
Thanks