A 1930 arrival in New York on the SS Saturnia by a passenger recorded as John Jeannopoulos, born 1899. The provenance — name, surname, plausible birth year — is consistent with the possibility that he was an older brother of Constantine’s generation, predating Takis (1911) by twelve years.
This record is currently the only documentary trace we have for someone matching that profile. Whether he was actually a son of Lazaros and Eftyhia, or an unrelated namesake, is an open question.