This is not my first foray into this topic here. It's just a matter of who knows and when.
First was my PCP, then a shipmate, then my wife, then my brother, bio-mom, and my kids. All went pretty well, except bio-mom said I'll always be her son. Well, she's 74 so I'll grant her the pass.
A couple of weeks ago I got a call from my true-mom regarding my recent knee surgery, and mentioned in passing that I was trans. She took it in stride, asking only if I was okay, and keep her apprised on what's happening with the rest of the family. I had no idea if she told my dad (almost 80) or not.
So Friday I mailed a letter to dad and gave him the basic information. Mail system is fast sometimes! I got a text message from him today, he's only concerned that I'm okay and to let me know that he loves me.

Sweet! This is going far better than I had hoped.
There's other aspects to family than direct support, and I'm shaking the luck tree so some of this might rub off on someone else who needs it.