The death record is probably either wrong or just not the right one then. Not all the trees cite the death record, and so it may be worth just going through them as at least some of the information provided could be accurate and assist in the research (at the very least in ruling out people/possibilities).
I looked at the actual 1900 and 1910 US Census pages noting the family in Quincy though and they both note that John Wray and his family were white. The names of the three surviving children were William b. Oct 1873, Thomas b. Jun 1876, and Robert b. Mar 1883. The 1910 record notes John's immigration date as about 1841, which is very close to the date noted in original post. Also, the 1880 census states that this same John Wray was a farmer and had additional children Mary (b. 1872) and Arthur (b. 1869) living at the time. Note also that the eldest son has the first name of the brother mentioned in the original post and that the second son has the same first name as the grandfather. John Wray's eldest daughter also had the same name as his mother. This could all be coincidence, but these look like family names to me.
This looks like a good match based on the information provided. If not, then can we get some clarification as to why (e.g., is Londonderry not the birthplace, is the wife incorrect, do the children not carry family names, do we know for certain that the man did not settle in Illinois, etc.)?
