Dad promises daughter he'll skip stepdaughter's graduation; goes anyway. AITA?

Is it okay to break a promise, if that promise was cruel to begin with? That's what one dad's hoping to hear, after his family drama exploded in a volcano of emotion. He took to Reddit's Am I the A**hole for opinions — and then to the comments to clarify, and to defend himself. But first, he wrote:

'AITA for breaking a promise and attending my stepdaughter's graduation?'

I’ll start by explaining some backstory. I (54M) lost my first wife when my son (25M) and daughter (22F) were ages 9 and 12. Both my kids took it as hard as you would expect and to this day have a poor relationship with both my current wife 'Doreen (49F)' and my stepdaughter 'Amy (18F)'.

I started dating Doreen about 4 months after my first wife passed, as such my kids believe I cheated on their mom. Amy was 5 when we got together and as such I see her as my own daughter.

On to the actual story, 4 years ago, two days before Kay's high school graduation, Amy got very ill while visiting her grandparents and ended up needing emergency surgery.

My wife and I rushed to be with Amy and admittedly I did not communicate well with Kay. At the time Kay didn't pick up my calls, so I left her a voicemail and several text messages explaining what happened and telling Kay I was sorry but I would make it up to her.

A few hours go by and I get a call from Kay, she is in hysterics telling me what a terrible father I am and stated that if I did not attend her graduation I would be dead to her. I chose to support Amy.

True to her words, Kay did not contact me on the day of her graduation. And when I came home, Kay's things had been moved out of the house with a note explaining that we were no longer family and to never contact her again.

Luckily, Kay and I were able to reconcile, however, I promised her I would give her absolutely anything in the world to make her forgive me. She said that she would forgive me as long as I refused to attend Amy's graduation as this was the only way to make it fair. I agreed at the time thinking she was just joking or angry and would soon forget.

This leads me to now. Invitations for Amy's graduation went out, and despite all the hostility, Amy wanted to make sure Kay got one. Kay called Amy later that day and said she would be unable to attend as she and I would be spending the day together per our agreement.

Amy broke down in tears asking me why I was missing her graduation. I assured her I was not and that I would speak to Kay. Later I explained to Kay that I simply could not miss Amy's graduation. Kay launched into a tirade about how I was a liar and an a**hole and how could I do this to her again.

I told her that we would talk when she calmed down and she said we would never talk again.

My son and several of our extended family have all taken Kay's side, saying I didn't see how hurt she was at graduation. My wife believes I am the a**hole for even promising that in the first place as I should have known it would only upset one or both girls.

And Amy is just sad and confused wondering why Kay hates her. I know keeping my promise and not attending Amy's graduation is probably the only way to salvage my relationship with Kay, but no matter how I look at it I would feel like I'm punishing Amy for having a medical issue, so am I the a**hole?

EDIT to add some relevant info.

I NEVER cheated on my first wife. your accusations are honestly tiring and disgusting.

Amy's Bio father was never in her life. I am NOT Amy's Biological father, that wasn't ever even in question as we are not the same race.

Amy had appendicitis, she was staying over 4 hours away at her grandparent's house. at the time that we left the only info Doreen's mother would give us was she passed out and wouldn't wake up.

My daughter was moved out of our house for about a month and a half after which we made up and she returned to live with us for another 2 years before going away to school.

I did not believe Kay when she said she wanted me to miss Amy's graduation as it seemed like a ridiculous request. despite what you all may believe our relationship was fine after this event we were in near-daily contact and she would frequently visit us.

As you can tell from the edits, the commenters had a lot to say. And they weren't on his side.

From angry-trans:

YTA. And have been for years. You are a bad father. Kay is correct. You are a liar. You've done nothing to prioritize Kay ever since your new family rolled in. Your relationship with your daughter is dead and the blood is on your hands.

From calliatom:

Seriously though... you never should have promised Kay that, knowing full well that you had no intention of keeping your word. And now you're being a bad father to Amy, too, by trying to use her tears and guilt to dig yourself out of the grave you dug yourself with Kay.

From victoria:

YTA - you replaced your kids mom with a new family 4 months after she died! Your kids lost their mom so young and you don’t seem like you prioritized their feelings or helped them deal with things, instead you moved on fast.

Kay didn’t have a mother to attend her graduation and she needed you there. Could you not have driven to the grad then back to the hospital?

OP got into it in the comments:

I didn't immediately move in Doreen and Amy once we started dating, we dated for over 2 years before we moved in together. My wife's death was not a sudden thing, she battled cancer on and off for years before she passed.

My children already knew/ were comfortable with Doreen as she was my late wife's best friend — so I thought they would enjoy having her around more.

I offered both children grief counseling, my son took me up on it, and I took Kay to a few sessions but she would kick/ scream/ cry every time I took her. Finally, the counselor decided that forcing her before she was ready would only worsen her grief.

I offered her therapy many times over the years, but she never took me up on it.

Angry-trans responded:

You actually thought that them being comfortable with the person being their mother's friend would translate to them being okay with her being their mother's replacement?

OP:

I never tried to replace their mother. To this day we keep her pictures and the decorations she made and picked out in our home. Doreen and I both love my late wife dearly. I thought my kids would enjoy having Doreen around because they did love her like an aunt before my wife passed.

Victoria responded:

Loving someone like an aunt is so different then being forced to love and live with a new “mom”

OP responded (despite many, many downvotes):

she never tried to be a mother to them, she tried to meet them on whatever terms they would allow her, but they outright rejected her.

Glittering-Bat353 brought up cheating:

So...if you dated for 2 years before you moved her in, but moved her in 4 months after your wife's death...you were in fact cheating?

OP responded:

we started dating 4 months after my wife's death, she moved in over 2 years AFTER we started dating. I never cheated.

But to some that's beyond the point. From Away-Breadfruit-35:

YTA, you are a proven liar. You consistently put your step daughter above Kay. You shouldn’t have promised Kay that at all, you knew you would not keep the promise but gave it anyway!

Why would you do that? It shows you don’t value keeping your word to Kay. Also, your step daughter is 18 — show her this post so she understands its you that is the issue, not her.

I also feel the graduation ceremony was the last straw for Kay, so there is probably a lot of missing info.