Bartholomew Kenny b. Co. Cork, 1823

I have Bartholomew in the 1880 census at Sheldon, Houston, Minnesota married to Ellen Moriarty.

I'm curious about both he and his brother next door listing their father as born in the US but they were both born in Ireland.

Their father is Maurice Kenny and mother Mary

Bartholomew b. 23 Dec 1823 in Cork Co. Ireland d. Jan 1912 Caledonia, Houston, Minnesota.

Patrick b. abt. 1820 Ireland.

Would like to know when Maurice's family came over and when/why he went back to Ireland.