My Trails into the Past

I have a census enumeration that has puzzled me for years. The head of the household in the 1900 Mitchell, Davison County, South Dakota, census is John Gleeson, my 2x-great-grandfather. With him in the household is his wife, Margaret, and children, Martin, William, Margaret T, and Frank T. Gleeson. These people are known to me and their information is consistent with other sources I have. There are also a woman and two children, Mary Frink, May Frink, and John Frink, listed as daughter and grandchildren, but I am not sure who these people are. Gleeson, John, w, m, Jan 1834, 66, mar. 40 yrs, b. Can, parents IR, imm. 1880, 20 yrs in US, no nat., rents, house.    Margaret, wife, w, f, Apr 1836, 64, mar, 10/10, Can, IR/IR, 1880, 20 yr    Martin, w, m, 21, son, Jan 1861, mar, 7 yr, Can, Can/Can, 1880, 20 yr, farmer,    Willie, son, w, m Jun 1874, 25, sing, Can, Can/Can, 1880, 20 yr, rr laborer    Margaret T, w, f, dau, sing, Jul 1876, 23, sing,...