Unfortunately sometimes information given in official records isn't accurate so I'm still doubtful that they had a child born in Ireland in 1859. That Detroit marriage makes it even more unlikely that any children were born in Ireland.
Tend to agree but could happen.
Marriage 3 October 1856
Marie born January 1859 (say conceived April 1858?)
(actually perhaps she lost a child between Oct 1856 and April 1858 and went home ......)
I'll keep looking.
1880 census says she was born in Ireland.
I will look at Andrew.....she may have followed him over to the US.
ETA From quick research it seems that there were other Ferguson families from Ireland residing in Michigan, some may be of the parents generation ie born late 1700s in Ireland.