Beauchamp-Braose Cat's Cradle

Corrected and reposted.

There's a very untidy mess in the upper reaches of Beauchamp of Elmley. MedLands gives the following configuration:

WILLIAM [I] de Beauchamp, son of WALTER [I] de Beauchamp of Elmley & his wife [Emmeline] de Abitot (-1170) m. Bertha de de Briouse, daughter of [WILLIAM [II] de Briouse & his wife Bertha of Hereford]
Children:
* William [II] de Beauchamp (d. 1197, m. Amice NN, had mistress(es) > son Walter [III] m. Joan de Mortimer
* Robert de Beauchamp (d. after 1209)
* Peter/Piers de Beauchamp (d. after 1194/95)
* John de Beauchamp (dates uncertain, may have d. after 1197)
* Walter de Beauchamp (named in only one charter, possibly an error for John)
* Emma de Beauchamp (d. after Sep 1192, m. Ralph de Sudeley, son of John de Sudeley & his wife Grace de Tracy)

Geni has two configurations, both faulty:
Maud Matilda de Braose (not Bertha) m. William of Elmley, 1st Baron of Beauchamp (and later John de Brompton, Sr.)
Son William de Beauchamp, Baron de Beauchamp m. Joan de St. Valery (not Amice anybody) Dates do not comport with what is known of William [II] de Beauchamp

Bertha de Beauchamp m. William of Elmley, 1st Baron of Beauchamp (not William; his parentage recorded nowhere in MedLands)
Son Walter de Beauchamp, III m. 1) Joan de Mortimer 2) Angharad N.N. (this is a generation too early)

MedLands admits that the chronology is dicey no matter how you look at it: "Given the birth of William [II] de Beauchamp’s children in the mid-1190s, it does not appear possible for their mother to have been the daughter of William [II] de Briouse. A connection between the Briouse and Beauchamp families is indicated by the claim brought by Amice (wife of William [II] de Beauchamp) in 1198 against William de Briouse, presumably identifiable as William [III] de Briouse. The implication is that the land in Oxfordshire, subject of the claim, was inherited by Amice’s infant son (on behalf of whom she was presumably acting) from Briouse ancestors. If that is correct, a likely explanation is that the land was inherited from the infant’s maternal grandmother, having been brought to William [I] de Beauchamp on his marriage. Nevertheless the chronology is not ideal, considering the dating of the marriage of William [I]’s father to before Aug 1114 (which suggests that William [I] must have been considerably older than his wife if she was the daughter of William [II] de Briouse) and the birth of his grandson William [II] in [1194/96].]" http://fmg.ac/Projects/MedLands/ENGLISHNOBILITYMEDIEVAL3.htm#Bertha...