George HW Bush lived from 12 Jun 1924 to 30 Nov 2018, thus living for 94 years and 171 days. This makes him the longest lived US President, surpassing the record of Gerald Ford (93/165).
However, another predecessor Jimmy Carter was born on 1 Oct 1924 and is still living. He is 94/61 today. If he lives for about 4 months more, he will surpass Bush’s record.
While on this topic, Donald Trump (at 70/220) is the oldest to take office as President for the first time. However, Ronald Reagan was 73+ when he took office for his second term and 77+ plus when he stepped down.
If Trump is re-elected in 2020 and completes his second term, he will hold these records.