Step-Dads diagnoses, talking between the two sides

Hi all, hope you are all well.

I posted this in the new comers section so I’ve simply cut n pasted it to this group.

My Mum and Step-Dad live around 2 hours away from myself and (nearly) any other family member. SD had been feeling ill for a few months and doctors found a growth that they ‘thought might be cancerous!” At the beginning of March, he was told it was and they gave him up to 10 years, then just over a week ago he was told it was more likely about 6 months.

The other concern is that my mum has been showing signs of dementia for a while and is slowly deteriorating. She is struggling to deal with this and things like cooking and cleaning are becoming hazardous as she is mixing things up or simply not realising something is wrong - eg - putting a laundry tablet in the dishwasher; looking around the room for her cat when he’s sat right next to her…

SD is not the easiest person to talk to about feelings, emotions etc, nor is he fully open about his plans, ideas or thoughts in general so trying to talk about this is feeling like almost a chore.

His children are involved and obviously their main priority is their dad, which I fully support and understand. My siblings and I have had very little contact with them over the years so neither side really knows the other.

I’m the youngest of 3 on our side but I feel I’m the only one really sensing the reality of the inevitable. 
I have a need to find out as much information as possible as soon as possible because, unfortunately, the reality is that he may not last even 6 months!

We have a WhatsApp group chat and I’m trying not to take over and seem like I’m giving orders as to who needs to do what and when etc but everything feels so relaxed and there doesn’t seem to be any sense of urgency to get things organised and I’m freaking out.

My mental health is going down the drain and anxiety has gone through the roof! My wife, a sibling and I went to see them yesterday and although we are in agreement that certain things need to be done sooner rather than later, trying to actually talk to my mum or SD is a challenge. He wants everyone to ‘act normally’ around him and he only gives us snippets of what’s going to happen. 

With all this, as much as I care for my SD, I need to plan for when he passes so we as a family know what their wishes are moving forward because I fear mum is going to go downhill fast and won’t be able to cope. 
My brother says I should chill a bit and focus on SD health and making him comfortable but there’s going to be a time when it’s too late to talk.

I don’t want to ‘take charge’ as I’m the youngest (and quite frankly, not that organised) but absolutely will if I need to but don’t want to upset anyone especially mum and SD but how do I start these conversations? Things like Wills (executors/power of attorney etc); his wishes, what is happening to their house and how to go about that….lots of things going through my head that I need to talk about for my own sake as well as making sure they are both taken care of but where to start? 
I understand everyone trying to remain calm and be supportive but these conversations need to happen, how do I even begin to talk to his children about this and then try to have these talks with mum and SD? Someone needs to take charge so to speak but I don’t want to step on their toes.

Thank you, *holding back the tears to type clearly*