Sorry, but your question is not clear.
However in your drawing there is no interaction between 5V generator and 12V generator. The first one only sees the R1 load while the other only sees the R2 load. This means a change in R1 will only affect the current of the 5V generator, and a change in R2 will only affect the current of the 12V generator
Inserting a third resistor R3, from the node R1-R2 to ground, it will share the current coming from both R1 and R2, so the two meshes will not be longer independent one each other. This means a change in R1, R2 or R3 will affect the current of both generators