Dear Abby: Can I reveal my family secret while my parents are still alive?

Dear Abby: My parents divorced nearly 50 years ago, when I was 11. Both of my parents remarried, though Dad is now a widower. A few years ago, Dad decided he couldn’t keep the secret anymore and shared it with another of my siblings and me. Our mom cheated on Dad for years, and our youngest sib, “Dana,” has a different father. At first, I was angry at her (though not surprised), but I’m calmer now.