Research Notes:
Peter Stewart stated on SGM, [1]
Nothing is known of the family background of Waleran's first wife, Oda. All we known of her for certain is that she was mother of five children by 1024 and after her husband unsuccessfully tried to get their marriage annulled she died as a nun at Notre-Dame de Coulombs by 1033.
Peter Stewart stated on SGM, [2]
Oda had five children by the time her husband Waleran of Meulan tried to have their marriage annulled, and she had died by the time he occurs with a second wife in 1033.
Adela (or Adelina) was evidently the eldest daughter of Waleran, as her
son Robert (born ca 1046) inherited Meulan. She was described a sister of Hugo, Waleran's heir, who was named as his son in the 1033 charter before the second wife. As far as we know Waleran had only two sons by his second wife.
Peter Stewart stated on SGM, [3]
I should have made clear that Hugo was definitely Oda's son - he named her as his mother in a charter for Notre-Dame de Coulombs dated 1066, see the copy made by André Duchesne here http://gallica.bnf.fr/ark:/12148/btv1b107216626/f48.item.r=Baluze%2038
"Hugo Comes Mellenti pro salute animæ meæ ... seu pro anima genitoris mei Comitis GALERANI, & ODÆ genitricis meæ".
This charter was misdated 1069 in the edition by Joseph Depoin (*Cartulaire de l'abbaye de Saint-Martin de Pontoise*, p 346) following the marginal emendation in a different hand, presumably because Waleran was living until December of that year - but Hugo was already count of Meulan by 1056, in his father's lifetime, and Indiction V as given by the scribe started on 1 September 1066.
[1] Newsgroup Post, soc.genealogy.medieval, Peter Stewart, in discussion "Oda de Conteville," 6 Dec 2016, [GoogleGroups_SGM].
[2] Newsgroup Post, soc.genealogy.medieval, Peter Stewart, in discussion "Oda de Conteville," 8 Dec 2016, [GoogleGroups_SGM].
[3] Newsgroup Post, soc.genealogy.medieval, Peter Stewart, in discussion "Oda de Conteville," 9 Dec 2016, [GoogleGroups_SGM].