Hi Reg--sorry for the delay, but I only just saw this post.
Agreed for the most part. Actually, there is another, more circuitous connection. Read what I wrote on the d'Aubigny project page at http://www.geni.com/projects/The-d-Aubigny-and-de-Albini-families-o.... (See especially the third paragraph on Adeliza Fitz-Osulf du Plessis and the honour of Belvoir). I'll copy here:
The d'Aubigny families (later called and spelled D'Albini, de Albini, Daubeny, and so on) were prominent Anglo-Norman families who originated on the Cotentin peninsula in Normandy. The two distinct families in Norman England were
(1) The d'AUBIGNY FAMILY OF ARUNDEL (also the "Pincerna" d'Albignys): the descendants of William (Guillaume) "Of The Isles" d'Aubigny, Seigneur de Saint-Martin-d'Aubigny, c. 1010-1068, believed to be a son of Néel (Neil, Nigel) I (III) de Saint Sauveur, Vicomte de Cotentin (St. Saveur). Guillaume "of the Isles" married Adeliza FitzOsulf le Freyne du Plessis, Heiress of Belvoir; she later married Roger de Tosny who became Lord of Belvoir.
Ironically, the d'Aubigny family that was to become the Lords of Belvoir was not descended from her through her d'Aubigny children, but rather through her de Tosny children, since it was her daughter Adeliza de Tosny's daughter Cicely Bigod (whose father was Roger Bigod, Sheriff of Norfolk and Suffolk) who inherited the honor of Belvoir and in marrying William "Brito" d'Aubigny (from the "other" d'Aubigny family; see below) he became Lord of Belvoir. Adeliza FitzOsulf's own grandson William d'Aubigny, on the other hand (son of Roger "Pincerna" d'Aubigny) became Lord of Arundel.
(2) The d'AUBIGNY FAMILY OF BELVOIR: the descendants of Main d'Aubigny, Seigneur de Saint-Aubin-d'Aubigné and his wife Adelaide de Bohun. This branch is often called the Albini Brito branch, since Main's son William "Brito" d'Aubigny (who married Cicely Bigod) was called The Breton, as was his son William "the Breton" d'Aubigny, who married Maud de Senlis. Through the inheritance of Belvoir via Cecily Bigod, who inherited it from her grandmother Adeliza FitzOsulf, this branch became Lords of Belvoir