What is your opinion about whether you are entitled to an inheritance from your parents?

Background:
– my parents have been divorced for decades
– I have one sibling and we are very close to my mom
– my father has been involved in our life and cares about us but has always been hands off and left all the upbringing to my mom
– we have a civil relationship with him but don’t really love him
– no one in the situation is rich, just middle class

My father recently drew up a will and told me and my sibling what it outlined. He wants to leave everything to his wife (not actually married but have lived together for 20 years) except for a small investment which will go directly to me & my sibling. His intention is that his wife will eventually leave everything to us since she has no children and we’re basically her stepchildren – she says that’s what she wants to do. Me and my sibling had different reactions to this news and I’d like to get other people’s opinions because I’m wondering if my opinion is in the minority. I was surprised by my sibling’s reaction, although I can understand it.

Sibling #1’s opinion:
Bad news. He should be concerned about our security and as such should give us an equal share. We deserve it because he hasn’t exactly gone out of his way to give us a lot during our lives. It’s his responsibility as a parent and grandparent. His wife may change her mind and not give us anything in the end.

Sibling #2’s opinion:
That’s fine. People should be able to leave their stuff to whomever they want and that wish should be respected. We’re not entitled to anybody else’s money, including our parents. We are responsible for ourselves and capable of paying our own way. Besides, his “wife” deserves it because she’s put up with him for several decades.