William Niven who was imprisoned in Dunottar Castle was my 8th great grandfather. Briefly, he was transported to America, eventually freed and made his way back to Scotland, but on the return journey the ship he was travelling on was captured by the French. After an exchange of prisoners he returned to Scotland to live with his family. He had one son that I know of who was also named William. This William married a Margaret Shiels and one of their daughters, Janet Niven, married Thomas Glen. I am a fifth generation Australian descended from this line. I believe another of his daughters married and went to Canada.
I have quite a bit of information on William Niven the covenantor and would be happy to share it with you if you'd like to email me.