illawarra on Family Tree Circles

Hi,
I am looking for any information regarding my grandfather and his family.
My grandfather, Michael MURTAGH, was born approximately 1867 in/around Kiltimagh/Woodfield/Kilkelly in County Mayo. He has several siblings. His eldest sister, Mary, was born 'dumb'. She trained as a dressmaker. There was also a sister, Bridget who married a man named Loftus. Thomas was another brother, who married a woman named Kate (Annie Murtagh lived with them, according to the 1901 Irish Census). One brother, John went to America, and had a son, John. I imagine that there are other siblings as well. My understanding is that Michael Murtagh grew up on a farm and it was called "Alcar"......apparently they were the first to have a slate roof (as opposed to thatched).
I do not know Micahel's parents name......there was some talk that his mother might have been a Costello before she married.....
If anyone has any information/suggestions for me regarding my search, I would be very appreciative.
Thank you
MM