I've read that apparently spouses will cower off to the side somewhere in the event of a giant or bandit attack or what have you, which makes sense for the ones who wouldn't be able to really defend themselves. What I want to know is, do follower spouses that should be able to help defend the home, like Mjoll or Vilkas, for example, fight back? Or is it scripted for all spouses to act that way regardless?

In general; whoever can fight will fight.

Mjoll my wife and Faendal my follower / house steward helped me fight random bandits when they attacked my home so it should be fine

I've only seen my housecarl outside during attacks. I have yet to see Vilkas around, though I know he does go outside. Just might have not met that certain criteria yet, my home doesn't get attacked much.

Ok, is Faendal a housecarl assigned when you became a thane or is he just a random follower? I am asking because I am wanting to know if only housecarls can become stewards or if any follower can.
I can't remember who Faendal is.

Sorry to hijack your thread Icedus.

Any follower can be your house, guard, thing.

Faendal is a follower, he can be turned into a steward. A housecarl is appointed to harass you until they die when you become thane of a location (locations that offers houses/plots).

Quite a few are unable to be your steward, actually. It seems entirely based on who Bethesda was able to get to record new dialogue.

He's the wood elf in Riverwood who is in a romantic rivalry with Sven over Camilla, the shop owner's sister. If you choose to help him make Sven look bad, you can get him as a follower, or you get Sven if you choose to help him make Faendal look bad instead.