Avraham Ben Matityahu Ashkenazi - Treves - Was Abraham the father of Yochanan?

N. Brüll (“Das Geslecht der Treves”. Jahrbücher für Jüdische Geschichte und Literatur 1 (1874): pp. 87-122) starts his genealogy of the Treves family with Yochanan ‘the German’. His son Joseph ben Yochanan was rabbi in Marseille in the 1340s. In those days Marseille was not yet part of France. After Jews were allowed to return to France in the 1360s, the family moved to Paris. Brüll does not mention any ancestors of Yochanan. Chaim Choneh (“From the Race of Rashi”. Sinai 10 (1942): 270-76) raises the possibility that this Yochanan ‘Ashkenazi’ was the son of Abraham ben Mattityahu from Treves or Troyes. The source for this Abraham ben Mattityahu is the Sefer Haneyar: “There was an event in the house of Abraham from Troyes during which he received from his father Rabbi Mattityahu, who [died in the 1380s and] is a grandson [or, more likely, a descendant] of Rabbi Mattityahu the Great from Germany, ...” (quoted from Choneh 1942, p. 173). However, historians identify this Abraham with someone else. Brüll (1874, p. 99) mentions that the Sefer Haneyar was written in 1392 for Joseph ben Mattityahu, a brother of Rabbi Yochanan ben Mattityahu (died 1429) and a great-grandson of Yochanan ‘Ashkenazi’, but does not mention the event in the house of Abraham of Troyes. Henri Gross (Gallia Judaica: Dictionnaire Geographique de la France d’Après les Sources Rabbiniques. Paris: Libraire Léopold Cerf, 1897, p. 242) adds an important detail: the name appears in a gloss or note added to the manuscript. Thus, the event in the house of Abraham was recorded after 1392. This “gloss could well have as its author Joseph ben Matatia, for whom the manuscript was copied towards 1392 ..., and this Joseph, brother of Yohanan ben Matatia, rabbi of Paris, is most probably identical with Joseph of Treves who was rabbi in Dijon. Thus, it would not be at all strange that he knew about the event which happened at the house of his relative Abraham. We can go even further. If this Abraham, as seems probable, belongs to a branch of the Treves family, it is very likely that he lived at Troyes, like Yohanan of Treves.” Thus, Gross thinks that Joseph ben Matityahu knew Abraham of Troyes personally. Therefore, if Choneh’s identification is correct, then Joseph would have known his great-great-grandfather! Perhaps, Abraham is another brother of Rabbi Joseph ben Mattityahu. Indeed, Brüll (1874, p. 242) mentions that Joseph ben Mattityahu had a brother by the name of Abraham. He is mentioned explicitly in an ordinance by king Charles V (1364-80) of France (Brüll 1874, p. 99).

So what is the evidence for Abraham being the father of Yochanan?