Been contacted about being beneficiary of 401k on estate

[momz54]

Kansas, I received a letter from an attorney representing a desceased exboyfriend. It stated that even though this person and I had been apart for some time (approx.10 years) he had apparently never changed his 401k at his employment to remove me as the sole beneficiary. His family had assumed his mother(now deceased) or two sisters were on there but they were not. His father was named sole heir to his estate by a court since he had left no will but passed 3 weeks after him. His father's wife had once said that her and her children (deceased step siblings) had no interest in his estate though they have no idea about this yet.

This letter is asking me if I would be interested in sharing or giving it all to his sisters. I am asking am I actually entitled to it all and if yes, can they fight me and actually win? When we were together, he never wanted his family on it because he said he wouldn't leave them anything. But he has lived with another woman for some time, but never married. The court ruled that they are not considered common law married either and she was not entitled to his estate except for creditor purposes only. So, am I entitled to the 401K he named me on 16 years ago??? and never changed?

It is yours--they could challenge it but it will be very difficult for them.