Georges Moustaki (Giuseppe Mustacchi) - Cousins

Hi,
From my family I am told Georges had a cousin called Benyamin (Binio) Moustaki, as a brother of Nissim (Nisso) Moustaki, also making Georges's grandparents Yaakov and Rika (Rivka) Moustaki.

Are there reliable ways I can really verify this information?

Thanks.