Charles de Gaulle. Apparently there was a proposal to share nuclear weapons between France, Germany and Italy, but according to the Charles de Gaulle government "atomic weapons should never be shared with others" (https://www.openstarts.units.it/bitstream/10077/15330/1/Nucl...).

De Gaulle wanted sovereign control of any French nuclear deterrent and did not trust that, if it came to it, the US would put itself on the line for Europe: https://www.nato.int/cps/en/natohq/opinions_139272.htm - presumably, for similar reasons he did not want any dependence on allies, even ones closer in location and likely part of the same conflict.

The US did actually help the French nuclear programme once it started going, under the reasoning that multiple nuclear-armed NATO members is better than one.

De Gaulle has long been out of power and dead. We're talking about current-ish policies and choices, and Macron did talk a few times about sharing the nuclear power and burden with the whole EU as France is now the only nuclear power left, but maybe it was just talk.