The only John Scantlebury found for Landulph is this one. From various internet sources (other researchers) it appears he was married twice, first in 1741 to Loveday Jeffry with whom he had several children, and then subsequently to Charity Triplett whith whom he had two children before she too died.
Parents of the John Scantelbuty christened in Landulph in 1718 are James and Honor.