Update: Me [26F] just found out that my estranged father has died. Do I contact siblings that don't know I exist or leave it be?

Link to original post: https://www.reddit.com/r/relationshi...ranged_father/
TL;DR: dad abandoned me as a child, had another two daughters after me that don't know I exist and today I found out he's died. Do I send commiserations or leave it be?
Okay so on to the update. So as I mentioned in the previous post, I had a liver transplant and one of the side effects of that is that I'm a heightened risk of developing cancer and it's kind of stewed with me for a few weeks because I knew my dad died of cancer but I wanted and needed to know specifics. I tried finding out without contacting any of the family but every point turned up empty. I decided that I needed to contact someone in the family and I sent a message through facebook to my dad's ex-wife and the mother of my eldest sister, I explained that I was sorry for her loss and that she could ignore this message but I'd really like to know what happened to my dad and if she could provide me with the details of his death.
Right, well, remember how I said that my sisters didn't know about me? I was so wrong, my eldest sister Lucy (22F) has known about me the entire time, she has photos of me from when we met at her birthday party, she had been begging our dad and grandmother for information about me and my address but had been rebuffed all the time because they didn't want my youngest sister Amy (15-16f) to find out, so Lucy had to keep me secret her entire life. Lucy's mum passed my details on to her and we've been talking the past few days and it's been amazing. We're so alike despite not growing up together and she's smart and funny and I'm so happy. I'm nervous about Amy finding out, whilst Lucy was well aware our dad wasn't perfect, Amy is still thinks the world of him and I will ruin that image of him in her head. And because of him forcing Lucy to keep me a secret, Lucy and Amy really aren't close because of how guilty Lucy feels.
Of course, I'm still angry, I'm in therapy and there's so much talk about with my therapist, I think finding out he put Lucy through so much too makes it even worse, we both have so many questions that we just can't answer and it's heartbreaking but we're working towards a relationship with each other without including him. I'm mad that because he felt he needed to keep me secret (why? It seems no one knows) has ruined the relationship between all three of his daughters, it makes no sense to me. All the adults know about me?? It's just bizarre.
I just wanted you guys to know because you were super supportive and helpful in my initial post! And I guess there'll be another one when/if Amy finds out I exist. Thank you so much. Sorry for rambling but I keep getting really emotional and I get really overwhelmed when I think about it.
TL;DR I contacted dad's ex-wife, reconnected with my younger sister who knew I existed all along and had been forced to keep me a secret and we're not working towards a relationship. Youngest sister still doesn't know I exist.
UPDATE on the update: Sounds like the entire adult family knew, Amy is the only one who didn't know but Amy's mum has always disagreed with keeping me secret so Amy will be told in the next few days. So I was a little sister for the longest of time and now I'm a big sister to two girls now??? So weird.
UPDATE #3??? So they told Amy today. She added me immediately after she found out. We're in a group chat and Lucy has named it sisterhood and I'm still an emotional wreck.


Source.