My house is 45 years old and has 12 gauge wiring with a 12 gauge ground wrapped in fabric. I have torn down some walls and want to relocate outlets in neighboring walls. Is it OK to use romex wiring that is 12 gauge but has a smaller ground wire? Can I connect these ground wires together, the 12 gauge and the smaller romex, in the line between outlets? So basically it is 12 gauge coming from the ceiling to an outlet, then romex connected and going out to another outlet, and so on to the end of the circuit. Do the ground wires have to be the same gauge or can they be different?

What brand of wire do you have? All of my Romex has a ground wire the same size as the conductors.

Just an FYI,

My parents house has romex with the ground wire smaller than the others. It was built in 1969.

It is out there but not on anything I've seen since.

Sorry, the romex is all the same size. The wiring in the house is 12 gauge with a smaller copper ground. The question is it safe to twist these different size grounds together in an outlet? The conducting wires are same gauge, but not the grounds. Is this code?

The first Romex made had a smaller equipment grounding conductor, and will work just fine.