Amar'e Stoudemire's Brother Allegedly Kidnapped & Beat Ex-GF ... Locked Her In Basement

Amar'e Stoudemire's younger brother was arrested in Kansas Monday night -- after allegedly kidnapping the mother of his child, repeatedly beating her and then locking her in a basement ... TMZ Sports has learned.

Law enforcement sources confirm ... 28-year-old Jerrel Stoudemire -- a former college football player -- was taken into custody around 5:30 PM in Hodgeman County, KS.

We're told ... officials believe Stoudemire went to the woman's home and waited for her to arrive. When she pulled up, he rammed his car into her vehicle ... and then pulled her out and beat her.

Stoudemire allegedly dragged the woman into the basement of the home and continued to attack her for several hours.

We're told the woman's daughter eventually found her naked and unconscious in the basement.

Cops were called ... and Stoudemire was tracked down and apprehended at a separate location.

He was booked for aggravated battery, aggravated kidnapping, aggravated burglary, aggravated assault and criminal depravation of property.