If his siblings can be determined this information would certainly bring a lot of us together in out connections.
The surname seems to be spelled both ways (but pronounced the same: Lay' den).
John married Ann Lynch (in atleast one instance she is called "Nancy")in Ireland (I am supposing).
To the best of my belief, although the spelling was sometimes Laden, it came to be Leyden as is in the case of my family's paternal side. I am wondering if any of his children continued using the Laden spelling.
Milltown Malbay, County Clare seems to be where some of their children were born (the last 2: Cornelius Joseph and Anna) on Kelley's Island, Ohio. Some descendants ended up in the Cleveland, Ohio area (as I was). If John Leydens siblings can be determined, this would certainly open up a lot of connections.