Question

If two bodies are in equilibrium in one frame,will they be equilibrium in all frame?

Answer 1

Since you have selected the topic as HEAT TRANSFER, I will assume that you are refering to thermal equilibrium.

Bodies in thermal equilibrium will have the same temperature. Temperature is degree of hotness or coldness and doesn't depends upon the frame of reference hence temperature difference between two bodies would remain the same in all frame of reference. Therefore two bodies in thermal equilibrium remain in thermal equilibrium in any frame.