Nothing much is known about the Knights Templar that is verifiable. The excavations of the Temple and the supposed find there etc are myth.
So, don't get talking about them to JW's who will go down the route of examing them and then debunking everything else you say.
The thing is, there are thousands of references, many many from highly respected sources about the date of Jerusalem's destruction by the Babylonians, 587/6 BCE is as well established as 1066 for the invasion of England by the Normans.
JW's DO NOT CARE ! The Holy GB says apples are oranges and JW's believe it.
If you ever are lucky enough to get a JW to honestly look at the 1914 doctrine, from examining Daniel Chapter 4 in an honest way, onward to being honest about the rest of it, the whole thing crumbles to nothing.
But for goodness sake don't let them be sidetracked by the Knoghts Templar or anything.