Yes, I think it is possible that my ancestor Jeremiah Canty was a brother of Michael Canty because Jeremiah was born between 1799 and 1801. You didn't mention Michael's birthdate, but if he was married in 1822, he and Jeremiah were contemporaries. However, we believe Jeremiah came from County Cork and we presume he was a farmer because he took up farming in Wisconsin. County Cork is adjacent to County Limerick, of course, and Michael may have been a Cork lad who decided to marry a Limerick lass.
Jeremiah's son Thomas, b.1830, married Mary Riordan, as you already know. I don't know the date but they were married after 1850 in the US. Her father was Timothy Riordan, b. 1794, and was a linen manufacturer in County Cork. I don't know the names of Timothy's siblings, nor his parents. I know only his wife's name, Honora Ryan. I know the names of Mary Riordan's siblings, but that would not likely be of help to you. If you're interested, let me know.