I believe this is the same person as this Leofwin:
Leofwin FitzAviet
Even though his date of birth is showing abt. 1095, everything else about him matches the Leofwin b. 1100 in the Overview notes. That being the case, the dates match exactly to the Leofwin FitzAviet at the link above. I think the father for Leofwin FitzAviet is actually Leofwin b. 1080 as the genealogy doesn't list anyone named Aviet, as far as I've seen.