NTA.
I've been in similar situations with my sister and my closet. Siblings can be a pain in the ass sometimes.
Get something like this for your console: https://www.amazon.com/dp/B0014ZXWCS/ref=cm_sw_r_cp_apa_fabt1_kVBSFb8MCVH45
If you use it, she won't be able to use your console without your permission.
Also, don't take the devices, take the chargers and they have to earn them back by being kind to the little ones for three days in a row. Since he sneaks them I'd take them home or get little locks to put through the plugs.
Why not just do this
Or buy this:
https://smile.amazon.com/dp/B0014ZXWCS/ref=cm_sw_r_cp_apa_i_I.gxFb3NG634M
I feel like it would be easier than figuring out wiring.
Unplug the TV and lock the plug. 17 bucks shipped and handled.
You could get the Breville and get one of these to lock out the untrained. http://www.amazon.com/Roride-RRKA-StoPower-Power-Plug/dp/B0014ZXWCS