Family knowledge and FTDNA Family Finder matches on my gr-grandfather's (Yitzhak Opinheim) line hit a brick wall in Brest-Litovsk, Belarus about 1825. YDNA matches and FTDNA's Iberian Ashkenaz project place his direct ancestor (name unknown) in Majorca in 1391. I have since added him to the FTDNA Xueta DNA project.
There are Family Finder matches between descendants (myself, siblings and 3 cousins) of Yitzhak Opinheim and a descendant of a Xueta family that lived in Majorca in 1391. This descendant has not responded to multiple emails about the match.
What to do? How and where do I look for a 434 years missing link? All suggestions - researchwise and DNAwise - will be appreciated.