I did a quick census search for these names:
1920 Milam County, TX (Precinct 3)
ED 122, Page 7B. Dwelling 153/Family 162
Jasper Smith, head, owned home free, white, 61, married, reads, writes, he and parents b Louisiana, Farmer
Lise Smith, wife, white, 51, married, reads, writes, she and parents b Louisiana
Henry Smith, son, white, 18, reads, writes, b Texas, laborer on family farm
J Smith, son, white, 9, attends school, reads, writes, b Texas
1930 Milam County, TX (Precinct 3)
ED 12, Page 6B.
Dwelling 122/Family 125.
Jay Smith, head, white, 22, single, b Texas, parents b Arkansas, Farmer
Jasper, father, white, 65, widowed, he and parents b Arkansas
Dwelling 123/Family 126
Henry Smith, head, white, 28, married, age 19 at first marriage, b Texas, Farmer
Nancy Smith, wife, white, 27, married, age 18 at first marriage, she and parentsTexas
Raymon (sic), son, white, 5, b Texas
Robert, son, white, 1 yr 1 month, b Texas
There is only one Monroe Smith listed in the 1930 census as living in Milam County.
1930 Milam County, TX (Precinct 1).
ED 5, Page 24A.Dwelling 85/Family 87.Rents home for $5
Monroe J Smith, head, white, 21, single, reads, writes, he and parents b Texas, bookkeeper for oil mill
It looks like Jasper and Lecia/Lise were married, and that she died between 1920 and 1930.Monroe is likely not their son -- he is not listed on the 1920 census and should have been.He could possibly be their grandson, if they had older children.