Guillaume / William d'Aubigny, seigneur de Saint-Martin-d'Aubigny - William and Niel's Birthdates/Death Dates Too Close Together?

Hello there,

I'm very hesitant to list Néel (Niel, Nigel) II (III) de Saint-Saveur, vicomte de Cotentin MP as William D'Aubigny's father since the dates of both birth and death are so close together. Of course, the birthdate for Niel is simply listed as "BEF 1016" but it seems suspect to me that is William was born in 1010, that this birthdate wouldn't be listed as before. It also appears they died around the same year which I know isn't too big of a deal but something feels off to me. Can anyone ease my concerns?