Hi Nikki
My mistake. I see you are speaking of Fredrih as having been born in the US.
One way to find out is find his birth record or baptism record in Sharon
Do you know if they were Roman Catholic or Evangelical (what we call Lutheran here in the US)? Checking the birth index for the Roman Catholic Church at Vukovar I don't see a birth of anyone with this surname from 1910-1912
Browsing these records I don't find LANGENEK nor KIBEL but
I do find KIEBEL
These records can be found online at Family Search. Also on Family Search are the military deaths for the years 1914-1916. I don't find his name in those years
The current online Croatia phone book finds 0 LANGENEK but there are 7 lisitings for KIBEL in Osijek County, which is adjacent to Vukovar County.
There is a web page for Danube Schwabian (as these Germans are called) which may be of help. The link below will take you to the page where the village coordinator contact info is listed, she may be able to help
http://www.dvhh.org/syrmia/village/wukowar.htmRobert