Hello Sveta,
first of all I'd like to thank you for spending so much time over my picture.
The captions in "Ein Photoalbum aus dem Hause Habsburgs" are empty, meaningless and full of mistakes. I guess the authors didn't know much about Friedrich's family, so they usually wrote "about" 1915 or 1910-15. So the picture we are talking about could have been taken some years earlier.
BUT: If the youngest children are Cäcilie and Franz, the picture must have been taken in about 1915, because Franz was born in 1912 and is about two or three years in the picture. This would mean, that Carlo (who died in 1912) can't be the boy next to Francesca. To sum up: Franz Salm-Salm and Carlo of Bourbon-Parma can't be in one and the same picture.
I guess the dark-haired boy doesn't belong to Friedrich's relatives. Maybe he was the son of some Hungarian count and friend of the family??
I have some other pictures of Friedrich's grandchildren:
The caption says: "Three of Friedrich's grandchildren, about 1910."
"Friedrich with Elisabeth, Natalie and Friedrich Hohenlohe, 1916."
"Albrecht with one of his nephews (which one?), Vienna 1917-18."
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By the way: Do you have pictures of Maria Anna's children you are willing to share? I would love to see them. Especially Francesca seemed to have been a very cute little girl.