Can we Connect two or more batteries of different voltage in parallel circuit?
Well, nothing would prevent you from doing that :)
To analyze what would happen, just draw the circuit diagram where you represent each battery as a fictitious ideal emf and a resistor with resistance equal to the batteries internal resistance in series.
What you find is that if the voltages are not equal, a current will always flow throught the batteries. The battery the largest voltage will be discharging, all the batteries may overheat and explode...