Duplicate display - correct?
You will need a video splitter. One video input cable, two video output cables.
Connections will be something similar to the following line diagram:
Raspberry Pi[Video Out] ------> VGA666 ----->[Video in] Video Splitter[Video out 1] --->VGA cable to crt monitor and Video Splitter[ Video out 2] ---RCA 3.5 mmm cable---> crtTV.
My thought would be a VGA based splitter.
One VGA cable in , and two VGA cables out. ( Versus a splitter with VGA in and one VGA out and one RCA out.)
Then you could use a VGA to RCA adapter in between the second VGA cable out and the VGA to RCA crtTV.
Examples:
Splitter -
https://www.monoprice.com/product?p...MIksLH0-jA6QIVD4_ICh3lzgO2EAQYASABEgK-VPD_BwE
VGA to RCA -
https://www.amazon.com/VGA-Cable-S-Video-Computer-Adapter/dp/B072Q35CSY
Again just presented as examples.
Details matter so create your own diagram and ensure that your requirements are being met.
Also - any need for audio?