Trans? Siblings Advice

Hi all! Thought I'd try the people of Reddit for some sort of advice. I've tried to be a bit more detailed so you can better understand our parents. I've put a soft trigger warning tag as it might upset some people as it's about how to come out to family. Sorry it's a bit long.

Advice I want is how I can best support and help them through all of this from people's experiences. And some suggestions of how best to include our parents in all of this too would be really helpful.

I have two siblings and one has messaged me saying that they believe that they're trans. They previous had said about being nonbinary a couple of months ago so I appreciate that gender has been an ongoing process for them.

I'm the eldest and our parents see me a bit differently to my siblings when it comes to all things and because of that I have their ear in a way my siblings just never have. I know that this will need to be used to help talk to parents about them being trans.

I know that when this starts coming out it will be hard, they are from a generation that finds a lot of this "gender stuff" annoying and my mum frequently quotes Sam Smith's "fisher-them" thing and rants about how dumb all that is. As I've explained to my sibling, our parents aren't hateful but they can be hurtful. While being from a different generation doesn't justify hurtful language, it does contextualise that this is all more confusing for them and it takes time.

I myself have gone through peroids of dysmorphia and had initially tried claiming I was genderfluid many years ago (by email lol) to our mother who kind of just brushed it off. I think its just hard for them to understand beyond binary genders (they may not understand transgender but man vs woman biological or not makes way more sense to them than fluidity and nonbinary, they also understand crossdressers are different). While I no longer identify as such now, I have retained a they/them/she/her preference and do have an ongoing relationship with gender myself. Similarly, I came out as gay a few years later to which our mother said good luck explaining that to your dad... Again, this pill has become easier as I'm bi since meeting my partner and I can fit into a heteronormative mold again for them. When we filled in the census a few years ago I stressed that I'm bi irrespective of who I'm with. I say all of of these examples as I'm the only one of the 3 of us who has had attempted these types of conversations with our parents - mum specifically.

When my trans sibling messaged me. I've straight away tried to be affirming and supportive. I don't care and will always stand by people if X is what makes them feel the most seen and validated. I did however state that as someone who has gone through gender dysmorphia and had friends who have transition and detransitioned I appreciate that this a huge thing that needs to be thoroughly worked through. I'm sure they are having all these feelings and thoughts but only talking to friends and watching reels about it all isn't enough to fully understand what you're thinking and feeling. I've recommended looking into gender dysmorphia focused therapy to help with this process.

They have got neurodivergency (as have I) and we are from a tough love type of household, so talking about thoughts and feelings is definitely underdeveloped in all of us. This is also why I think talking to someone who knows this stuff properly would be helpful.

While none of this is about my feelings, it is a bit worrying because I just want the best for them and in our current society there is a lot of trans hate and I know that it won't be an easy road. If it is the road that feels right for them, then we can go down it, bumpy or not, but I just want them to be thorough with this and understanding themselves. They're only 19 and all of this has only really started coming to light since going to university and meeting much more diverse people. Not a negative, but we are all influenced by our peers for better or for worse sometimes. I know they have a new close friend that I believe is also trans. I just want to add for clarity they have always been the type of person who gets sucked into other people's interests and hobbies "they like this, now I like this" and it's always been an all or nothing thing.

In terms of advice, I guess I just want to know how I can best support and help them through all of this from people's experiences. And some suggestions of how best to include our parents in all of this too would be really helpful.