When WW II broke out, the 2d Cavalry Regiment was sent to Arizona, still on horses, to guard the Mexican border. When they returned to Ft. Riley, the horses were left in Arizona and the unit inactivated, men and equipment sent to the 9th Armored Division where several other units were formed.
One of the units to eventually come out of this was Company D, 89th Cavalry.
When 2d Armored Cavalry Regiment left Ft. Polk April 2005, their 4th Squadron was inactivated, men and equipment used to form 4th Brigade, 10th Mountain Division.
So you have two branches in the family tree, brother!