One way to accomplish an end run around a research "brick wall" is to study the siblings of the ancestor who has us stymied. While this technique will not always provide the answer we'd hoped for, it can sometimes lead to valuable information.
Right now, I'd really like to find more information on the family of my second great-grandfather, Franz Jankowski. I already know that Franz had married Franziska Olejniczak—but I knew this only because of their mention in their daughter Marianna's own marriage record. I have not yet been able to locate their own record—if, indeed, the names were entered (or transcribed) correctly for their daughter's wedding.
Still, from their daughter's record, we can see that Marianna was likely born about 1862, somewhere in Poland. That, however, was the age given for Marianna in the transcription of the church record, which presented her as a seventeen year old bride. Looking to the civil record presents a different picture. In that record, Marianna was listed as being ten years older, which calculates to a year of birth in 1852.
That earlier date might have been a less problematic issue, had I not discovered a collateral line for my great-grandmother. Scouring the marriage transcriptions listed online at the Poznan Project, I discovered another daughter of Franz and Franziska named Stanisława. This daughter, according to her own marriage record, was not married until 1894. According to the civil record, she was born in 1871.
It was encouraging to find a sibling for Marianna, one whom I could—hopefully—trace through the decades to see whether any further mention might be made about her parents and other family members. And that I did, following Stanisława and her husband, Franz Janczak, from their home in Żerków, part of present-day Poland, to a new home in Buffalo, New York—until research stalled with her early death and some puzzles about her children, of which I had already written.
The problem, though, was in some dates. Noticing Marianna's issue with the disagreeing dates of birth—either 1862 or ten years earlier—made me wonder about a sister born almost ten years after that later date, in 1871. Yes, that large a time span could be possible, especially given larger families of that era. It could also hint at a birth order for Marianna's siblings, possibly putting her at the top of the list. It would be helpful to find any indication of other siblings in the family line.
Thus, back to the Poznan Project to see whether I could locate any other marriage transcriptions listing those same two parents for either a bride or a groom. There was one: a woman by the name of Antonie Jankowska, daughter of Franz and Franziska. Even younger than Marianna's sister Stanisława, she was about to become bride of Joseph Karcz in 1898.
Above inserts: transcriptions of marriage records for members of the Jankowski family in Żerków, Poland, courtesy of the Poznan Project.