Black Crow is one of the many subsidiary teams of Genesis. There are 20 members (all of which are children) and are led by the Thunder King Nue. All members are Gravity Children that do not know anything about themselves, including where they were born. In chapter 169 of the manga, Nue stated that even though he doesn't agree with the Takeuchi brothers' methods, Black Crow would still work under Genesis so that they could live normal lives.
All of the team have very strong ties to each other, seeing themselves as more of a family then a team. Nue acts as an older brother and protecter to the younger members, stating that he "want[s] to make sure their futures are filled with nothing but happiness".
In battle, all of the members wear what appears to be a smaller version of Nue's own Regalia, whether these AT suits can produce a current on their own is yet to be seen, but they can share out the current created by Nue's Regalia, sharing the burden out onto all of the members, rather than Nue taking most of the stress and allowing Nue to use the powerful Direct Current abilities of his Regaila.