Probably not a direct descendant - the dude was born in Cornwall, and Quaker William's great-grandfather had owned an estate in Wiltshire (if *his* branch of the family also came from Cornwall, it must have been some generations back). But they were most recently of Bristol.
"Penn" is more than likely a good old Cornish name ("By Tre, Pol and Pen / Shall ye know Cornishmen").