http://fmg.ac/Projects/MedLands/NORMAN%20NOBILITY.htm#_Toc254886761

HONFROI de Tilleul and his wife ADELINA de Grantmesnil had [two] children: 

a) ARNAUD de Tilleul . Orderic Vitalis records that "Drogo filius Goisfredi de Novo-Mercato et Rogerius Erneisi de Coluncis filius nepos Guillelmi de Guarenna et Ernaldus Unfridi de Telliolo filius, nepos ex sorore Hugonis de Grentemaisnilio" donated revenue.

b) [ROBERT of Rhuddlan . Orderic Vitalis says that he was nephew of Hugues de Grantmesnil. The editor specifies that he was the son of Honfroi de Tilleul, but the primary source on which this is based has not yet been identified.]