Matilda de Muscegros

Death of John son of John of Monmouth and Agnes de Muscegros An Inquisition taken in 9 Edward I [1281], at Gloucester, by the oath of Nicholas de Gamages, knight, Elias de Heydone, William Geraud and others of county Gloucester, found that John de Monemuth, who was hanged for felony, held the manors of Lassindon and Bolleye, in co Gloucester, of' his mother, Agnes de Muscegros, and his sisters, Matilda de Muscegros', Joan and Amabilla, who enfeoffed him.[1]

I think that Joan Neville and Amabilla ? are from the first marriage and are 1/2 sisters to our John de Monmouth the younger.

Reference

https://www.wikitree.com/wiki/Monmouth-4