I am also researching this line of the Ryan family, as James Ryan (b. 1844) was also a son of Stephen Ryan and Catherine Casey. He is listed, with the family, in the 1850 Quincy Census and the 1860 Briggsville, Marquette County census. I also have a death certificate for James Ryan that lists Stephen Ryan and Catherine Casey as his parents.
I am hoping you have new additional information since your original post. I am willing to share any information that I have as well.