I don't mean like the one that is created from clone vouchers, I mean like your sim in every way (same skill progress, relationships, etc.) I'm just wondering if it's possible, it's ok if it isn't and I'm just forgetting that.

Save the household you want to clone to the saved bin in Edit Town. Then place them in your town.

I would recommend getting a mod that allows you to edit family relationships, though, in case the game glitches up. When I cloned a family, the game recognized both versions of their daughter as belonging to the original mother. I had to use the master controller to fix it, and even that took a few attempts as the game resisted the changes. O.o

1st way : Easy way
You will see the menu "save your household"click "without houses".
Then you save your households at the specific skills you love your sims to have in the library.
This way you can move them into any town any time you want.

2nd way: Complicated way
There are mods which can generate homeless and NPC only from your library sims.
So sorry that I can't remember which one beside Twallan's.

Hope it helps.

Another way is to have the SIM go to a mirror and have them "Change their appearance". Once in CAS, you will be able to "Save the SIM" onto the SIM Bin, which is where all the "template" SIMs are found.

The mirror thing only saves their appearance, not skills or relationships.