Inheritance Dispute With Step-Siblings

AITJ for not sharing my inheritance with my step-siblings? My grandmother passed away 6 months ago

and left me $50,000 in her will. I was really close to her growing up and she helped raise

me when my mom was working two jobs. My dad remarried when I was 16 (I'm 24 now) and his

wife has two kids from a previous marriage. They're 19 and 21. They only met my

grandmother a handful of times at family gatherings and honestly she never really bonded with them.

Now my stepmom is saying it's "unfair" that I got inheritance and her kids didn't get anything.

She thinks I should split it equally between the three of us since "we're all family now."

My dad is staying neutral but I can tell he thinks I should share at least some of it.