You are right, Willis' Father James H. was from Indiana
Willis is found in Harris County Texas in 1870 living with James (his father and listed brothers and sisters at that time) Willis was less than 1 year old at the time of the 1870 census
James H and Willis older siblings can be found in Indiana in the1860 census (Rutherford, in Martin CO) The last name Blagrave, is written down in 1860 as something looking like "Blackgoare". Probably why it has been tough for some to locate in Indiana.
But William Scott, Mildred(Milley in 1870)and Young James H. are all listed with James (The same brothers and sisters enumeerated with Willis in 1870 in Texas)