Question

How do electrons repel each other in multiple bonds?

Answer 1

Your premises are mistaken..........

Explanation:

A typical `C-C` bond is `1.54xx10^-10*m` long; a `C=C` bond is `1.45xx10^-10*m` long; a `C-=C` bond is `1.38xx10^-10*m` long.

The more electrons between the carbon nuclei, the closer they can approach each other WITHOUT internuclear repulsion. And the average bond enthalpies reflect this interaction; certainly this is observed for `C-=C`, `""^(-)C-=O^+`, and `N-=N` bonds.