According to CP Dugdale made an error in the d' Aubigny line and if
Burke used this as the source it could account for the discrepancy.
From CP Vol I ARUNDEL
1 William d' Aubigny 1st Earl d 1176
2 William d' Aubigny 2nd Earl d 1193 <<- missing from Dugdale
3 William d' Aubigny 3rd Earl d 1221
4 William d' Aubigny 4th Earl dsp 1224
4 Hugh d' Aubigny 5th Earl dsp 1243
4 Isabel d' Aubigny
1 John FitzAlan
+Isabel d' Aubigny
2 John FitzAlan (?6)(awarded rights to Arundel by right of his desceased
mother but the FitzAlans were not known as Earls of Arundel until the
death of the widow of Hugh d' Aubigny)
+ Maude le Botiller
3 John FitzAlan (?7)
+ Isabel Mortimer
4 Richard FitzAlan 8th Earl of Arundel
+ Alasia de Saluzzo
5 Edmund FitzAlan 9th Earl of Arundel
+ Alice de Warenne
6 Richard FitzAlan 10th Earl of Arundel
+ Isabel de Spencer
+ Eleanor Plantagenet
Merry Xmas
--
Simon Pugh