Here is the GEDCOM file I have at this point. I have also created this fan chart that shows some of the contents of the file, but not all.
As I have entered some of the stories I have found other names that are not in the GEDCOM file, so I'm sure someone has a more up-to-date copy.
But here is what I have for what it is worth.
The following two newspaper articles are the only written information we have found about Henrietta Janes Cox and her son, Isaiah Cox, Jr.
ISAIAH COX, PIONEER TO DIXIE IN 1862, REACHES 85TH MILESTONE
Monday June 5th, marked the 85th milestone for Isaiah Cox, acclaimed as the first white child born in Mt. Pleasant, Sanpete county, Utah. Mr. Cox has been ill for a month, hence the celebration of his anniversary was limited to a dinner for immediate family members.
Born June 5, 1859, in Mr. Pleasant, his parents were Isaiah Sr., and Henrietta Janes Cox, early LDS converts and pioneers to Utah in 1847. The family came to Utah's Dixie cotton mission in 1862, when Isaiah was scarcely three years old. He learned early the business of pioneering, and drove a team before he was in his teens. He was one of the boys who helped to gather the small black rocks from the ridge west of town to be hammered into the immense underground marsh on which the great white temple of St. George was erected.