First off I am J1. I descend from the Grahams of Scotland. My family is the biggest family in the Graham DNA Project. The project believes that our family is the progenitor family of the name and descendants of Sir William de Graham born 1128. It is believed now believed that William de Graham may have been Flemish rather than Anglo-Norman. It is believed his father could have been Arnulf de Hesdin a Flemish Baron who entered England with William the Conqueror. Second, our closest relatives(based off of the J1 DNA project at FTDNA.com) outside the Grahams belong to the Baloch tribe. We share an SNP with them that is about 2500 years old. That means the earliest we could have split from them was 500BC. The Baloch speak a North-west Iranian language. Some scholars and linguists believe that they are descendants(at least partially) of the Parthians. The Parthian Empire was founded by the Parni tribe, the Parni tribe came from the Dahae federation of tribes, and the Dahae federation of tribes is partially descendant of the Massagetae tribe. Another tribe that is partially descendant of the Massagetae are the Alans. A map of 500BC shows how close the Massagetae and Dahae were settled to one another. Third, the only non Germanic tribe that was a part of the Great migration into Europe were the Alans. One of the groups of Alans lead by a leader named Goar settled near Orleans in Gual, which is just South of Flanders. This is the best explanation I have come up with and it may explain your situation as well. J1 is not common among Iranian groups but it is consistently found within them. It probably explains most of Western European J1 which is rare. I am curious to know what sub-clade of J1 you belong to. The Grahams in the J1 project on FTDNA.com have been waiting to find a closer match within Europe I meant to copy this ( I'm not used to this format yet !! )