Margaret Mulvaney : Short Biography

I am hoping someone will be able to help us further the lineage of our Irish ancestors who immigrated to Canada around 1828. 

Margaret Mulvaney was married to Edward Roe AKA Rowe (in Canada).  According to Canadian censuses, she was born in Ireland in either 1798 or 1801. 

According to a 1901 census where we find Edward's and Margaret's granddaughter, Cordelia listed with their son, Michael, who was recorded and then crossed out, stating that he was deceased.  In that same census, we learn that Micheal probably immigrated to Canada around 1828.  At that time, Michael would have been between 2-3 yrs old.  We don't know what happened.  Did Edward come to Canada alone and then had Margaret later join him with their 3 living children:

Bridget -- baptized on 9 aug 1819 at Kells, Meath, Ireland (Mom's Mother's name)

Deceased baby John - baptized 9 May of 1821 at Kells, Meath, Ireland and then died on 21st June 1822 at Ballenthopen, Kells, Meath, Ireland (Dad's father's name)

Mary -- born or baptized when ???  She is found in a marriage record dated 20 jun 1836, in Buckingham, Quebec, Canada (Dad's mother's name)

Michael -- baptized 8 may 1825 at Rath, Nobber, Meath, Ireland (Mom's father's name)

The next son has the name of James. The tradional 3rd son to carry his own dad's name is missing.  Why?  Was there another son who died? Could he have been born during the trip to Canada?

The details and other reasonings I have are posted at https://www.wikitree.com/wiki/Mulvaney-87

The other children that we have found for this family are:

Margaret, Elizabeth, James, Catherine, George and Sarah Jane.  No birth or baptismal records found for any of them.  Just census or marriage records.