After Mackay died, his son George William went back to Canada via Hong Kong. In 1911 he and his wife returned and opened the Tamkang Junior High School. He continued living there even after he retired. When he died in 1963, he was buried on campus in a tomb next to his father.
在淡水出生的長子威廉，於父親過世後，由香港回加拿大深造，一九一一年，威廉偕同夫人回到淡水，創辦淡江中學，退休後他仍賦居淡水，直到一九六三年過世葬於馬偕墓旁，和他的父母一樣，把台灣當作永久的故鄉。