I'm not sure what to make of all this, I've just picked up my MORGAN line research again and thought the following from the OP was MY family!:
1900 census usa: daniel, plains, luzerne, coal miner, immigration 1884
1910 census usa: daniel, plains, luzerne, coal miner, married, boarder emigrated 1880. no ann in it.
1910 census usa: patrick, plains, luzerne, b 1883, married, 2 stepdaus, emigrated 1890. no trace of him after that.
no trace of prince or pierce.
I have the personal name Pierce in my Morgan line so it makes sense, but like the OP, I could not find "Prince" after the 1910 PA census. It could be that he died.
I'm very interested in what anyone has found about this, as I knew my MORGAN's had settled out in that general area of PA (then some moved slowly west toward Berwick, PA, at least one married an O'BRIEN and moved on to OHIO). But I also found my grandfather's marriage certificate and it states that his father was from out in Plains, PA.
I'm just so excited to see this thread on MORGAN. My MORGAN'S have been very elusive thus far, I assume it is because they moved around to where the work was.