By Katelyn Polantz, CNN

(CNN) -- An alleged member of the Oath Keepers will plead guilty on Wednesday to charges related to the January 6 insurrection, the first plea deal among the Capitol riot cases against extremist groups, a notice filed in court says.

Graydon Young, a 54-year-old from Florida who went by "GenXPatriot," is charged in a 16-person conspiracy case alleging members of the Oath Keepers plotted to carry out the January 6 insurrection.

It is the first guilty plea among any defendants in the major Capitol riot conspiracy cases and is a significant development as investigators continue to pursue leads on extremist groups that they believe planned for an armed attack to help then-President Donald Trump and stop Congress from certifying the 2020 election.

Young is among a pair of siblings charged in the Oath Keepers case who investigators say traveled to a Virginia hotel to attend pro-Trump rallies in Washington in early January.

Prosecutors allege he applied to become a member of the Oath Keepers group, a far-right coalition of largely ex-military and law enforcement that organized paramilitary training and attendance at political events, before January 6, and was posting on Facebook about recruiting for the group in December.

Prosecutors say Young was part of the "stack" military-style formation of Oath Keepers that cut through the crowd to move inside the Capitol.

It's not yet known if Young will agree to cooperate in cases going forward, but it is likely he has spoken to investigators as part of obtaining his deal.

He is currently charged with six crimes, including conspiracy and aiding and abetting the obstruction of the congressional proceeding. Those may be reduced to fewer counts with his plea deal.

Prosecutors also previously charged him with document tampering after he allegedly deleted his Facebook account two days after the riot.

Young's co-defendants in the case are contesting their charges.