Looking for Karl Heinz Keuger Born IN 1922 OR 1924 Oplen Germany Now Poland

Can anyone give me some tips on how I might find info about my mothers family?. My mother Engelina Ingrid Kruger GAlloway died in Boise IDaho USA 6 years ago.

She had a twin brother bron 1922 o 1924, a mother KAroline Kronkenmyer and father KArl Kruger born about 1898 and livedn on Oplenstrauss - I gues that is a street.

I have never known these people as my mother woudl not speak of them or her life in Germany and am trying to find if maybe my mothers twin brother has children. I want to connect with them and do gnenology about the family.
Otherwise I have no relatives nor extended family and nothing to tell my kids about theri realatives.

Any tips on how I might proceed without travleing to Ooplen - Upper SILesia to look around woudl be lovely Thank you
MAry Ellen Galloway HAley
San JOse, CAlifornia USA