My John was born in 1807 in Washington, Franklin County, PA. I think that's Washington Township. He did have a son named Joseph who was born on 07 OCT 1847. I am not sure where, but probably Lawrence County, Ohio. The family moved there around 1840 and then on to Ironton, Lawrence County, Ohio in 1842.
I don't have a Robert Alexander. It looks like from what you wrote that Robert could be a brother of John.
I did my DNA test through ancestry.com and I'm waiting for the results. This might shed some light on my Alexanders.
Hopefully, I'll have it soon.