if beneficiaries of life insurance policy have been deceased and it goes estate can anyone else contest it?

The answer is the same whether your beneficiary has died or is still alive. There are several valid instances for contesting an insurance policy designation. Some states have what is considered communal property laws and if you live in one of these states, and you failed to name your spouse as a beneficiary, the surviving spouse can certainly request that he or she receive the policy money. But, even if you don't live in a state with communal property laws, a spouse, an ex-spouse or your children can contest the insurance policy payout. If these circumstances arise, it is likely to go to the courts for a final verdict on the matter but indeed, just because a beneficiary has died doesn't mean that the proceeds automatically go into the estate without question.