Seeking Family of Margaret Sheehan, Child of John and Mary. Limerick

I have only two documents related to my great-great grandmother, Margaret Sheehan: 1) her death notice in the San Francisco (California) Chronicle, and 2) her marriage record.

1) Margaret died on 29 Oct 1894 in San Francisco.  The notice says she was 55, so that indicates a birth year of 1839, and that she was a native of Limerick.  The notice states that she was predeceased by her husband, is survived by 4 sons and a daughter, who my 90-year old aunt remembers, and two siblings, Maurice Sheehan and Mrs. Ellen Fouts.  The notice also says, "(Boston (Mass) papers please copy),"

2) Margaret married Edward J Fallon (d. 1885, San Francisco, CA) on 4 Nov 1860 in Brookline, Massachusetts, a town that's part of Greater Boston.  Margaret's parents are identified as John and Mary Sheehan, and the witnesses were Michael Moloney and Mary Sheehan.

Margaret's birthdate is questionable, though her obituary indicates 1839.  The age shown on her marriage certificate is illegible, and could be  27 (= b. 1833) or 21 (= b. 1839).  On Censuses, her birth year could have been 1832 (on 1870 Census) or 1840 (on 1880 Census).  That's a range, so somewhere between 1833 and 1839.

I believe I have definitively found Margaret's sister, Ellen Sheehan Fouts.  Ellen Sheehan was the sponsor at the baptism of the first of Margaret Sheehan Fallon's children, Margaret T. Fallon, who was baptized on 13 Feb, 1863 in Brookline, Massachusetts.  Margaret's second and subsequent children were born in San Francisco, California, beginning in 1869.  Ellen had come West sometime prior to that, and married Abraham Fouts on 3 Feb 1866 in Sonoma, California.  She appears on the 1870 and 1880 Sonoma area Censuses; those indicate that she was born between 1845 and 1847. Ellen lived the remainder of her life in Sonoma, had 5 sons and 1 daughter there, and died on 9 April 1899. 

Maurice Sheehan continues to be a mystery.  There were several in Boston at the time of Margaret's death, but I have no clues about him at all.

And I have been unable to find a John and Mary Sheehan who parented the three identified siblings, Margaret, Maurice and Ellen. In fact, the only couple I could find named John Sheehan and Mary, who had a child named Margaret in Limerick in 1839, was John Sheehan and Mary Mahony.  This Margaret was born in Freemount, Limerick and Cork, on 18 Jan 1839.  There was also a Margaret Sheahan born to John Sheahan and Maria Dea in Croom on 29 Jun 1829.  That couple also had a son, Maurice, born in 1840. 

Mary Sheehan, named as a marriage witness, is potentially a sibling, as well.  Such a Mary J Sheehan lived in Brookline, Massachusetts for the 1865 and 1870 Censuses.  She died on 16 Jan 1901 in Cambridge, Massachusetts, another town that's part of Greater Boston.  Extrapolating from her death record, she would have been born in Ireland, about 1834.

There are potentially other siblings who had passed prior to Margaret.  For example, a "Missing Firends: Irish Immigrant Ad" ad appeared in the "Boston Pilot."  It related the search of Hannah Sheehan, then living in the R. C. Orphan Asylum, San Francisco, seeking her brothers John and Maurice Sheehan of Boston.  This is speculation but might help someone familiar with the family.  

So, I can speculate until the cows come home, but mayb Margaret's story will ring a bell with someone.  I hope to visit Margaret's birthplace on a trip to Ireland one off these days.  Thanks so much!