Mignon's son Peter though looks much like Nando (mostly the ears) i really do believe Carol, Elisabeth, Mignon and Nicholas were Nando's. Ileana, I'm not so sure of since she is dark compare to her sisters and well Mircea is not Nando's.
Nando must have felt uneasy and distant towards Ileana and Mircea. Mignon was his favorite. i really do believe she was his.
Missy most have slept with both at the time. I also i dont blame Missy for having lovers since her husband treated her like a mistress then a wife.
the unknown child in 1898, was Zizi's child. Stillborn or not, no one knows what happened to that child. It would be forever remain a mystery.