I am one of three sisters whose father left us in 1960, and he remarried in the 1970's. He was only in contact with our eldest sister, until dementia made it impossible for her to continue contact. We were told that he had died on 17 August this year, and that he had been cremated with no funeral service. He leaves a wife and a stepson (who was around when our father left us in 1960) who is definitely not his son.
Can we lay claim to his estate? I am thinking more of when his present wife dies, than an immediate claim. This way, when his wife dies, her son wouldn't be the only benefactor, and we would be able to have an inheritance from our father.

It depends on the state of his estate. If he willed is property to someone, that person gets it. If he had no will, most states automatically will everything or most everything to his surviving spouse.

Your best bet is to contact a probate lawyer and see what the situation is. Its *possible* that you make be awarded something.