That's the part that you can't tell from the census. You don't know if he's the wife's brother or a husband of the husband's sister, or the husband of Emma's sister.
Social Security Death Index about Robert Kruml Name: Robert Kruml SSN: 480-09-0845 Last Residence: 59911Bigfork, Flathead, Montana, United States of America Born: 2 Mar 1907 Last Benefit: 59911Bigfork, Flathead, Montana, United States of America Died: Jun 1987 State (Year) SSN issued: Iowa (Before 1951)
Montana Death Index, 1860-2007 about Robert Kruml Name: Robert Kruml Age: 80 Estimated Birth Year: abt 1907 Death Date: 3 Jun 1987 Death County: Lake Residence County: Lake Social Security Number: 480090845 Marital Status: Married Or Separated (Married) Index Number: 2872
Source: Montana State Genealogical Society
I think he might be the husband of a sister, because his parents were born in Bohemia, and that's not true of Neff or Emma.