So, I received a response letter from my dad, apparently a few days after I sent the letter (Delayed mail? Me not checking my mail often?), I thought it was worth retyping:

24 June 2016

Dear [my first name],

Thank you for the letter you sent me a couple days ago.

I appreciate it very much, and I’m flattered, that you care enough about my opinion to send it.

I’m a child of the sixties, and my cultural conditioning tells me that polyamoury leads to trouble.  That may or may not be true; but it still makes me a bit uneasy when you talk about your new boyfriend and it develops that he’s married.  I worry that your loving heart could lead you into heartbreak, unpleasant scenes, disaster.

However, your mother reminds me that you are an adult, a smart and well-educated adult, and undoubtedly more in touch with the cultural zeitgeist than I am.  And of course, I have to accept the truth of that.  So I wish you the best of luck in your romantic endeavors.  Keep your mother and me posted; when you’re happy we’ll be happy along with you, and of course we’ll always be ready to provide unconditional love and support if anything should go wrong.

Your loving father,

Dad

I think this shows hope – my dad can be a bit, well, behind in his thinking sometimes. But the thing is, I know his intentions are good.  There’s room for growth here – my thought is that the Dan Savage approach here is probably best – keep exposing them to it in a “this is part of my life, part of me” kind of way so that they can see how happy this makes me.  It becomes something they get used to over time.

What do you think?  Good approach?  Could use work?