Yes, Sheridan was a diplomat's child, so they moved around quite a bit. Round about his 18th birthday he was in a position to go visit the Dalai Lama. Now unless there are orange blossoms in India/Tibet (depending on whether or not the Tibetans have gotten loose from China at that point), Sheridan's family must have been a bit mobile.
And David Sheridan's comment about "people here like us, Lord knows why" seems to indicate to me that the elder Sheridans are not native to that area, but are recent, if welcome, arrivals.