How to make two players control the same GameObject?

Hello everyone! I'm currently working on a 2D scroller/platformer game in which the players can control a spaceship and fight enemy aliens.

Currently, my game is single player only and I want to add a multiplayer mode. However, I don't want the second player to use another instance of the GameObject, I want both of them to have the ability to access the spaceship and control it. In other words, they'd need to work with each other to guide it in the right direction and avoid the obstacles.

I'm a fairly novice Unity user (I only started using it a month ago) but so far, all my google searches seem to point in the direction of the NetworkManager. I watched a couple tutorials about it, I get the gist but I'm still lost as to how I can use it to my advantage and make my two players control the same GameObject.

Any help is appreciated!