My apologies. I thought my collection of material on the execution of Thomas Doughty contained more information about his family. Alas, only his brother John is mentioned in the sources I have. You have more information on the family than I.
John Doughty, younger brother of Thomas Doughty, was also on this ill-fated voyage. The Doughty brothers were among ten gentlemen adventurers along for the ride and riches. John Doughty apparently returned to England after his brother’s execution and didn’t continue with Drake. After Drake’s return to England, John Doughty attempted to have Drake prosecuted for murder, but he himself was thrown into London’s Marshalsea Prison, accused of plotting to have Drake kidnaped and turned over to the Spanish king.
The New England Historical & Genealogical Register, Volume 1, April 1847, Page 126 has an article regarding the passengers of PELICAN, Drake’s flagship, later renamed Golden Hind. Other sources include National Geographic Magazine, February 1975; Sir Francis Drake by James A. Williamson, Archon Books, Hamden, CT, 1966; Sir Frances Drake by George Malcolm Thomson.