I also found Orville Agnew (brother of Marshall Sr.) in the 1930 census in Butler County as well. It appears that he is now married to Marshall's wife Elizabeth!! They show children as : Ruth age 9 (1921), Betty age 5 (1925), and Orville age 5 months.
So....sometime between 1920 and 1930. Marshall and Elizabeth divorce. Marshall marries Mrs. Edna Fitzpatrick (she has two kids from previous marriage. Elizabeth marries Marshall's brother, Orville.
According to the census records (and other records): Norman was born @ 1918 Ruth was born @ 1921 Marshall was born 1923 Betty was born @ 1925 Orville was born @ 1929-1930.
It is pretty safe to assume that Norman was the son of Marshall.... and Orville Jr. was the son of Orville Sr. But...Who was the father of Ruth, Marshall and Betty? Marshall or Orville? Where were Norman and Marshall in 1930? Adopted out at this time? But why these two children and not the rest? I love a mystery! I will keep digging!