I am picking up on the story told in Changing Tack. Catherine Kelly married Patrick McHugh in Michigan, before moving to Missouri in 1873 with most of their children. One daughter, Anna, stayed behind.
Anna McHugh stayed in Michigan with her Aunt Susan. The 1880 Census reveals that Anna was born in Michigan in 1857. This provides a clue to the date of Catherine’s marriage to Patrick McHugh. It seems reasonable to speculate that Anna might have been the oldest child. As yet, I have been unable to find a marriage certificate.
Susan Kelly had married Jeremiah Cronin, a native of New York. Susan’s date of birth comes out as 1833. The oldest child of the marriage (Francis) was born in 1860 in Michigan. Also in the household were a nephew, Theodore Kelly (born 1863 in New York) and a niece, Jessie (born in 1870 in Nebraska). Unless there is a strange coincidence at work, in that Jeremiah’s sister married someone called Kelly, then Theodore and Jessie must be John Kelly’s children.
In searching through the records it is clear that there were hundreds of men called John Kelly who were born in Ireland. Identifying the right one is almost impossible. It would have been good to work out his date of birth. Even finding the exact dates for the birth of Theodore and Jessie has proved to be more difficult than I thought. I don’t have access to Ancestry’s American records. Perhaps they contain the answers.
The 1860 census reveals the presence of Patrick and Kate McHugh, both aged 30 (born 1830), in Detroit. Their children are Ann (Anna?) 6, John, 4, and Mary, 1. I can’t find them on the 1870 census. According to the information that I have been given, they should still be in Michigan.
It was also difficult to find them in 1880 in Missouri. Having tried a number of variations of spellings, I came across a family under the name Mc Cune. 
Patrick’s date of birth now comes out as 1823. Catherine is 10 years younger than her husband (born 1833). Mary is now 18 (should be at least 20). The other children are Susan (16), Thomas (13), Andrew (11), Heber (?) (8) and Frank (6). There is no sign of John. He would have been 24 and could well have been living independently. It should still be possible to find him though.
Whilst there are many more people called Kelly than there are called McHugh, there are far more variations of the spelling of the McHugh name. This makes it difficult to be sure that I have found the right ones. The search goes on!