Did widower Presidents always re-marry while in the White House or afterward?

 No

Widower President Thomas

Jefferson did not re-marry - -

his daughter served as

White House hostess;

widower Andrew Jackson

also did not marry after

FLOTUS Rachel's death.

Martin Van Buren and 

Chester A. Arthur entered

1600 Pennsylvania Ave.

as widowers and opted not

to "let wedding bells ring". . .