In addition to Jenna's answer, there are some "ways and means": if the one deceased in 1917 livedin Paris (my village!) even grave could be found! All Archives are closed for this long "week end" and the National one will be, after june 18th (computer's sickness) but "where is way is a will" :send me direct e mail if more wanted. I will have a look in naturalization records. Regards to your family!