Unfortunately for you, if your father never legally divorced his 2nd wife,
she is still considered his wife. Secondly, if he told you that he wanted you and your siblings to be the beneficiaries of his estate, you should have asked for a copy of the insurance policy and made sure that it reflected his wishes.
This is why it is important to review and update all documents with a qualified attorney to make sure the legal papers reflect the wishes of the testator.
Check with the insurance company to see if your father amended his beneficiaries at a later date or if a Separation Agreement was executed between them in which she agreed not to claim any interest in his estate or insurance policy.
Leonard Weiner, Esq. Divorce Solutions