Would this be the first time ever that the same 2 people would be rematching in the US election?

John Adams and Thomas Jefferson, 1800 and 1804.

John Quincy Adams and Andrew Jackson, 1824 and 1828.

Martin van Buren and William Harrison, 1836 & 1840.

Benjamin Harrison and Grover Cleveland, 1888 & 1892.

William McKinley and William Jennings Bryan, 1896 and 1900.

Dwight Eisenhower and Adlai Stevenson, 1952 & 1956.

No it will not. It happened in 1892 with Grover Cleveland and Benjamin Harrison.