The William Buteau that I look for is actually the one you found in the Canadian Census of 1881, his father is named Elie and his mother Genevieve Readman.
Jacques, Joseph, Laura, Sophie and Marie are all brothers and sisters. William is the only family member that I cannot track anymore.
I searched everywhere to find him in Canada, but without success. So I turned on the U.S. side and I found William Buteau that could correspond.
The problem is that I need a real proof that this exact William Buteau living in U.S. is the exact same William Buteau born in Canada. The only way to know that this is the same William Buteau is by having a confirmation of his parents name which I cant find in the records marriage ou death.