What part, if any, he played in the Percy revolt of 1405 is not clear. However, he became a ringleader of the Southampton Plot in 1415, which aimed to murder King Henry V in Southampton before he sailed to France, and replace him with Edmund Mortimer, 5th Earl of March. However, Mortimer revealed the plot to the King, and the conspirators were promptly arrested and executed.
He married Alice Nevill, daughter of Ralph Nevill, 1st Earl of Westmoreland, c. 1401,by and they had eight children:
Elizabeth Grey born c. 1402 and died in 1454, married Sir Roger Widdrington
Sir Thomas Grey born c. 1405 and died in 1443, without issue
Sir Ralph Grey born in1406 and died in 1443, married Elizabeth Fitzhugh and left issue
Joan Grey born c.1408 and died in 148, married Sir John Salvine
a daughter born c. 1410, married an Arundell
Margaret Grey born c. 1414, married Gerard Widdrington