Question

For analogus organs is it neccesary to have a common ancestor

Answer 1

not necessary .... can depend on

Answer 2

analogous organs are the ones which are having same functions but different structures of their organs. for eg. wings of butterfly and a bird.
the analogous organs are also the one which are provided to have convergent evolution.
therefore, it is not necessary for them to have a common ancestor as these organs are preferred to be same in function and not in origin and ancestor.