Board Thread:General Discussion/@comment-3048593-20130509225000/@comment-61371-20130514011843

Most, if not all, Captain Britains are likely Corps members, given that Merlyn or Roma handpicks them (mostly. The Faiza Hussain in Avengers Assemble #15AU might be an exception, but given the current state of the Corps post-Uncanny X-Force...who the hell knows?). As of the publishing of the Handbook ADour mentioned, every Captain Britain who appeared before its publication is included as a member (or damn near every one, including 1610 Brian), either in that Handbook or in the "Updates" section of the paperback rerelease (which is more recent and adds 161 Brian, Ultimate Jamie Braddock, 9105 Brian, 10091 Brian, 57780 Brian, 98193 Brian and 98193 Betsy).

I think, at one point, I went in and added Corps membership to everyone listed in the Hardcover version.

While Artful Dodger has a good point about not assuming every Wolverine is a member of the X-Men, the Corps is an inherently Multiversal group, and it's probably an instance where we CAN assume membership. We just can't assume every Brian Braddock is Captain Britain or that every Captain Britain is a member of Excalibur or the Avengers, since not every reality will have an Avengers or Excalibur (but the Corps isn't limited to any one reality, and exists as a group outside all realities).