I'm not related, just trying to give a little help.
I search the 1870 CENSUS for Joseph Davis and found that if this is the correct Joseph Davis you are looking for - the census indicates he married in May of the census year (1870) to Mary.And the son Horace or looks like it is written as Harris on the census is already age five.So perhaps Joseph and/or Mary both were marred previously and the child is from one of those marriages.It lists Mary's place of birth as C. W. - and it says that Horace's or Harris' mother is foreign born.I have no idea what C. W. may stand for.GOOD LUCK.Hope this helps a little.
1870 CENSUS, Benzie Co, MI, Joyfield Twp, Joyfield post office, enum 28 July 1870, page 1, HH 12/12
DAVIS, JOSEPH,31, male, white, farmer, value real estate 1000, value personal estate 125, born PA, married within the year in May
DAVIS, MARY, age 23, female, white, keeping house, born C. W.,, father and mother foreign born, married within the year in May
DAVIS, HARRIS (?), age 5, male, white, born MI, mother foreign born
JOSEPH DAVIS & FAMILY IS LIVING NEXT DOOR TO THIS DAVIS FAMILY SO THEY MAY BE RELATED IN SOME WAY:
DAVIS, WILLIAM, age 55, born PA
DAVIS, MILDRED, wife, age 45, born VA
DAVIS, WILLIAM, age 13, born PA
DAVIS, ALMA, age 10, born OH
DAVIS, HENRY, age 7, born OH
DAVIS, JOHN, age 4, born MI
DAVIS, GEORGE(?), age 1, born MI