The Gifford/Giffard Family and its allied lines have been extensively researched for many additional generations. It includes John I and Henry II, William the Conqueror, Kings of England, Charlemagne, et al. If further information is desired it is available in the references listed below.
Weis. p. 109.
NEHG "Register." v. 71:170, 171, 175; v. 74:231-236, 268; v. 75:132-136;
v. 136:98-103.