Mike and John Dwyer of Ireland, Michigan and Minnesota

I'm looking for more information about my Great Grandfather John Dwyer and his father "Mike" Dwyer.   John Dwyer's death certificate from Duluth, MN on Dec 22, 1912 says John's father was Mike Dwyer born in Ireland and John's mother was Martha E. Baker of Ohio.  The only Martha E Baker I've been able to find is from PA.  John was born in MI and married Emma Oven Disberry in Michigan. John and Emma had two children Clifford John and  Earl Joseph both born in MI.  They moved to MN by 1895 where they had a third son my grandfather William Roy Dwyer.  He went by Roy Dwyer.  There also seems to be a Mary A. Dwyer who signed John's death cert rather than John's wife Emma.  I seem to have hit the proverbial brick wall.