Such a powerful and frustrating story. It's heartbreaking how tradition can override basic fairness and the care given by family members. The first son rule you described causes so much pain, especially to those who provided real support.
This is why documenting family history and wishes properly is so important. For anyone wanting to research their heritage or create clear family records, it helps to check https://myheritage.pissedconsumer.com/review.html resources first.