A lot of North West Europeans are J2, some clades of J2a coming from Roman or Jewish or Celtic people , some J2b2 clades coming from a lot of sources, you guys here need to learn that your direct male line is not what defines who you are
Maybe 80% of the man in your family from the down of time are R1b , but the rest could be everything , it changes nothing and it means nothing in terms of self identification
Congrats on your cool and not common in your part of the world male line
There is J2 from early middle ages ( 1 a and 1 b I think) from The Netherlands
Here some guys said that the people were Avar mercenaries or something, but it could come from a lot of sources in NL