Alexander II's illegitimate son Joseph Raboxicz

[Hania4921]

Does anyone have further information about Joseph Raboxicz born about 1867-69. The mother was Princess Lubomirska.
I am trying to find out where he was born. I am trying to confirm information I already have. I have reason to believe that he was adopted
by a family in Poland which were cousins to Alexander the II.
Any information would be greatly appreciated.
Hania