To leave holiday early even if it will upset my dd?

Stay with your daughter. Please don't mess up your relationship with her. She has probably kept thoughts to herself and now she has actually got you to herself on holiday and you say you are leaving all her frustrations and hurt have come flying out. Take this from someone who has always felt second best to an ill sibling. His dad is there and he's 18.

OP literally says he did it to himself.

I bet there are other times your dd wanted to show you something or talk to you or even unburden herself as a teen and was pushed aside.

She’s going to hold that drinking session in her head a long time. Newly given birth and I’ll assume you was meant to be helping her out and ds1 has a turn.

Now you’re away with her with the very same baby and ds1 has a turn. It’s going to feel like anytime your attention turns to her/her child ds1 suddenly has a turn.

Look deep about all the times you’ve been helping either of your other two children even an important conversation or an educational one and suddenly ds1 has suddenly had to become the centre person. I bet it would add up.

For those who do not understand what dka is:

Dka is when the blood turns to literal acid. It can kill within hours.
It cannot be from eating to many sweets like implied here. It's from lack or no insulin or a sick bug it creates ketones. These ketones can get large enough to kill.
It can end t1ds in hospital on insulin drips or in the ICU. It causes extreme thirst like thirst you have never experienced. It shuts down the organs within matter of hours. It can cause blindness, organ failure etc.
It cannot be from to many sweets. So stop being arrogant.

It's basically the same as self harm. Those who go into DKA willingly need mental health help.

Both of these.

It feels strongly like there is also manipulation by him here. He is in hospital and has a parent present. It's unlikely he will be able to harm himself while there or before you return.

He has to learn not to use his illness to manipulate, and that it has to be managed no matter what else is going on in life.

Rushing home to baby him is unlikely to help him, and very likely to push your daughter further away.

Yabu stay and support your DD. Your attention seeking DS has his dad there.

As pretty much everyone else has said, stay. Remember you have 3 children not 1. Sounds like he has had more than his fair share of time and attention.

Definitely stay. Your daughter is sending you a clear message, I’m guessing she wanted you after she gave birth but you chose to be with him?

He’s an adult. The girl sounds unhinged but he is choosing to go back to her time and time again.

I think this is a divide and conquer situation. He's got his dad, his phone, facetime. He and his dad need to work their way through this. Staying away also would send the subconscious message that you know they can handle it, which will be good for DS. He HAS the support in place through you both, without you cancelling the holiday.

Using T1 diabetes as a form of self harm is a recognised thing. In the short term it can cause DKA which can be life altering/fatal in the long term it can cause chronic health issues alongside the T1D. Yes it is self inflicted but it’s also a cry for help. Maybe you would see it differently if he was cutting himself?
All mental health conditions could be seen as ‘selfish’ in terms of how it affects the rest of the persons family but that’s just how it is.
I speak from experience as the mum of a now 25 year old T1D who was diagnosed at 5 and has been through similar. I also have another child who had to sometimes be patient.
having said all that I don’t think the OP should go home just yet as he is in hospital and has his dad.
A little bit of understanding that it’s not just a case of ‘eating too many sweeties’ would help though.

Can you afford to easily recreate the holiday - in terms of costs, annual leave etc for you, your daughter, her partner and your grandchild? If not, you shouldn't consider leaving unless his life is in danger. He sounds like a very selfish person, and you seem to be enabling that.

Type 1 diabetes

Diabetic ketoacidosis

This ^
also I wonder if you coming would make things worse for your DS. You need him to realise that he is an adult and it’s on him to manage his condition. Adding you to the conversation at this stage might make him less involved in a way.

I would go back and be with my 15/18 year old, and your daughter is 25 and a mum herself/has a partner.
It's strange how many people without a disability/illness moan about the attention being on those who do. People have have to suffer one say they'd give up all the attention in a heartbeat and are sick of "normal" people not being grateful.

Well I don't think she is. I do think the son is manipulative and looking for attention though.

I don’t think some readers realise how serious type 1 diabetes is and the long term implications of diagnosis. It is a very challenging diagnosis, for teens especially, to deal with.

its a very tough situation for you OP and I can certainly understand your desire to go home.

She'll have remembered it.

I feel stuck between my 2 children

But your DS is with his father. I suspect your DD has been overlooked for the last 5 or 6 years in relation to your focus on your son's condition. Stay, and enjoy your DD's company. If you leave, she'll know where she is in your affection & priority.

I would love to understand the 3 letter acronyms to be honest.

Also your DD needs to grow up. She has a baby yet acting like a teenager. Not worried about her brother being in dka more worried about her hoilday being spoilt. I mean seriously?

But it’s not is it? It’s obvious from OP’s post it’s a manipulation tactic

Unless he takes a turn for the worse or is literally at death's door, then you need to trust his Dad is
a) on it
b) will let you know if anything changes
Your DS wants to be left alone and has stated this.
Your DD wants you there and has stated this.
She will not forget if you leave now and then you will be looking at LC/NC.
You are not being asked vocally by your son to choose. You are being asked by your daughter to put her first on this occasion. Do that.

Go home chiefark and get him mental health help
The diabetes team will have a psychiatrist he can access. The poor lad needs help.

I did something similar in my early 20s and I’m glad my family were there to support me, I haven’t repeated it since

Am I the only one who things your dd sounds like an immature spoilt brat. She's 25 ffs with her own child. You would think that might give her a a little insight into how worried you are about your ds. It's not just that he's diabetic but that he seems to have triggered this incident with low mental health. I woild go home and tell dd to grow up.