I don't have much information on Christian and Julia yet. Until I read your post I only knew their names from the 1925 Iowa Census where Henry listed them as his parents. I didn't know they had died young - or when or where they died at all.
After reading the bio on John H. Sienknecht from 1905 I did a little more investigation and I think I've found the Ruge family in Germany. Did Joachim Ruge come to the U.S.? I found a Joachim Ruge who died in Fort Dodge, Iowa, in 1919, who I believe could be their uncle. As soon as I can I'm going to head to the State Historical Society of Iowa and look up his obituary in the Fort Dodge Newspaper to see if I can get any clues.
What I do have a lot of information on is John's brother (my great-great grandfather), Henry Detlef Sienknecht. I have many newspaper articles, dates, documents and photos I'd be happy to share. I would love to have the same information on your side of the family.
I recently attended the Sienknecht Family Reunion in Lincoln, Iowa, and no one knew "Grandpa Sienknecht" had any siblings in the U.S.!
Here is my email address:
jason.staker@gmail.com Please email me with your contact information and we can begin exchanging information and hopefully filling in holes in the family history.