Welcome. My name is XXXXX XXXXX would be glad to assist.
You stated" I would add a junction box (actually two in order to insert some slack into the existing 12/2 line) between the GFCI outlet and the second outlet on one of the 12/2 branches"
It sounds like you are getting power from the GFCI itself before it gets to the 2nd receptacle. I would want it before the GFCI
The TV does not need to be GFCI protected
I understand; I wasn't really trying to provide that protection to the TV.
Now, with that said, one thing to know, is the kitchen is supposed to have 2 circuits for the counter tops with nothing else on them, that is code today. Your addition will work, but wanted you to be aware of requirements.
If you have 3 circuits now on the kitchen receptacles, then you will still be in compliance
I assume that it would be better to add a junction box on one of the 12/2 legs (and prior to the GFCI) rather than just splicing my new romex into the existing junction (i.e. with the 12/3 and existing 12/2 legs).
you could wire directly into the existing junction box
no reason to add a box unless there is no room for additional wiring, too cramped or something
Plenty of room in the existing PVC box; I just didn't know if it was an issue with the 12/3 setup.
no, it is no problem and perfectly fine. That 12/3 setup is called a MWBC, multi wire branch circuit. Where you use a single neutral to supply to circuits.
The neutral is shared with the 2 hot wires.
Saves on initial wiring costs
So I would have 2 black from 2 of the 12/2 (including my new romex) joined to black of the 12/3; 1 black from the other 12/2 joined with red of the 12/3; all 4 whites joined and all 4 grounds joined. Correct?
Your new romex would connect: Black to EITHER the black from the 12/3 or to the red of the 12/3. Not both. (unsure if that is what you mean?)
all whites are together and grounds also, yes
Correct. I correct the new 12/2 black to either the 12/3 red or 12/3 black. Thank you for your help.
yes, you have it. you are most welcome, glad to assist