Here are the specifics for the two households. BOTH were enumerated July 29, 1870, and they're written with the same handwritting so I assume the enumerator was also the same:

Shelby County, TN, District 2
Page 21 [41], Household (1)53, Family (1)53
John MASON, age 40
Bettie, age 29, born in MO
Henry C., age 13
Peter, age 11
George, age 9
Ellen, age 7
John, age 5
Caroline, age 3(?)
Jesse, age 10 mths

Shelby County, TN, District 2
Page 23 [42], Household 168, Family 168
John MASON, age 37
Lylia, age 28, born in TN
Henry C., age 14
Peter, age 12
George, age 10
Ellen, age 8
John Jr., age 6
Caroline, age 4
Jesse, age 2
Elizabeth, age 57


***The occupation of the 57 year old Elizabeth is listed as "with son". So maybe the mother and her son actually had two separate houses, and the son somehow got listed as being in both?

***On the next census, in 1880, only one of these MASON families is listed (and they're in the same district). Also interesting and that the wife is listed as Lyddia, and being born in Missouri. On the 1870 census, wife Bettie was listed as being born in Missouri and wife Lylia was listed as being born in Tennessee. So maybe these two wives were actually one woman that went be two different names?

***Or maybe these were actually two separate families that just so happened to share so much in common, and one of which who just so happened to completely "disappear" before the next census 10 years later? :-)
:-\