This is the information I received from St Mary's parish Athlone
John Brown/Mary Dalton Address: Coosan, Athlone, Co. Westmeath, Ireland
Children: 1. Bridget born 19th Nov 1826
2. William born July 1839
3. Thomas born 12th May 1842
4 Margaret born 23rd Sept 1846
Michael Browne/Elizabeth Wansboro. Address: Coosan, Athlone, Co.
Westmeath., Ireland.
Children: 1. Thomas born 3rd Jan 1858
2. Mary born 11th Sept 1863
3. Michael born June 1867
4. Patrick born 11th Feb 1872 (Mother was recorded as
Catherine Wansboro)
Maybe I have just had a lightbulb moment but in my last post I made a comment about Elizabeth maybe died and Michael married a Catherine as shown in the 1875 Kansas census....ummmm.
Well looking at the info from St Mary's I pasted above MAYBE I am correct and MAYBE Michael Brown had a second wife Catherine who could have been the sister(or rellie) of Michael's first wife Elizabeth.
Now to try to find death or marriage in Athlone, Westmeath....but that will have to wait till tomorrow and I am in need of sleep.
Thanks to JJ and Polarbear for giving me information that has helped to think outside the square...

But even if this lightbulb moment has some substance it still does not explain why Granddad Mike Brown does not show up on any census