Robert Newton usually was referred to by his middle name, Newton, or simply Newt. If Newt was born in Virginia, we then can place the Turpin family’s arrival in Indiana between his birth in 1821 and 1839 when his mother purchased land or 1842 when he is married in Indiana.
A marriage record is found in the Owen County, Indiana records:
Robert Newton Turpin to Sarah Elizabeth Lowery, 1 May 1842
Newt would have been 21 years old when he married.