This NN person is being shown to separate the children from the traditional view that their father was Giselbert, Comte de Roucy (I00020519). Ebles succeeded Giselbert and is documented to have the siblings shown. Thus, this fatherhood was widely assumed. Giselbert's wife was conjectured to have been a daughter of Guillaume III de Poitiers and Adela de Normandy in order to explain the name Ebles.
A more recent conjectures suggest the children are those of Ebles de Poitiers (I00020505), younger son of Guillaume IV de Poitiers and Emma de Blois, a daughter of Aubry II de Macon and Ermentrude de Roucy, Giselbert's sister. That could explain the rare name Liétaud, whose appearance as both the father-in-law of a sister of Gisbelbert de Roucy and a brother of his successor is striking, the name Eudes and the succession to the Blois lands of Rumigny and Coucy. [Reference] _'La Succession au comté de Roucy aux environs se l'an mil', in 'Onomastique et Parenté dans l'Occident médiéval'_, by Jean-Noël Mathieu.