I need two sources one is 5v for microcontroller and other is 6v for relays, I am using using battery of 12v. I have to two ic's 7805 and 7806 to regulate voltage.
My question is can i use them in parallel?
Basically, yes you can. Worth bearing in mind that regulators in parallel are like transistors in parallel, i.e. one can become a current hog which may not be a positive aspect, however I wouldn't worry about that as you're powering two different loads, so really you're paralleling two subcircuits.
Mind the recommended minimum input and output capacitance values for BOTH regulator applications - depending upon the individual circuit loads you might get away with only selecting for the larger of the (2) input capacitors, but it is best to use (2) separate capacitors and keep them close to their respective regulators.