Rains County was formed from Hunt, Hopkins, Van Zandt and Hopkins Counties in 1870-------so checking in these counties prior to 1870 would be a good place to look for your families.
 
 It is always a good idea to know which counties border the county where you are searching for your families.  The reason being, is that first of all, county lines do change.  Also, moving back and forth over county lines happened quite a lot............Also, check on when the county was formed and from what county or counties it came from.  Looking for your folks in a county prior to that county's formation would be fruitless........check out surrounding counties for resources also.