Ok but consider time
We all know that Lance is homesick and we were shown just how far away they were from Earth at one point. But something that hasn’t been considered is that time is passing differently for them than it is on Earth. A good representation of how this is is in Interstellar, when the main character’s youngest sends him a video, something that she refused to before and only decided to do because it was her birthday. The birthday marking her the same age as her father. Another example of this is if you take a clock and you do one revolution around earth the time on the clock is different than the time on the clocks on Earth that would have previously been running at the same time. I don’t know the exact science so that might not be exact.
So like… I have an idea for an au where Lance’s family is devastated when they find out, and Lance’s 13 year old genderfluid sibling is like ‘I want to go to the Garrison’ and Lance’s parents and everyone else are like 'No, we just lost Lance, why would you want to do that’ and the sibling is like 'Lance’s dream was to make it to space and if he couldn’t get there in his life time then I’m going to do this for him’ so they take up engineering and physics to try to get into the Garrison. They try to get in at age 14 and don’t, but try again at 15 and do. They get an opportunity to be a pilot because someone quit. They have to deal with Iverson and he’s like 'You’re just like your brother, useless, a replacement because someone else isn’t here’ and they realise that this would have fuelled Lance’s anxiety and he never told any of them. They make it their personal mission to be problematic, but also the best in their class. Like, insulting Iverson everyday, becoming 50000000% more petty and salty, and even at one point challenging him to a rap battle. On a separate occasion they somehow manage to barge into a staff meeting to shout that at Iverson that he verbally abused and degraded their brother’s mental health and worsened his anxiety, before presenting a petition signed by the whole student body and some parents to get Iverson fired. Iverson is fired. After a few years the Kerberos mission is being rebooted. At age 19 they are chosen to pilot. They tell their family that they’re finally getting to see space. The team includes Mrs Holt, who had stepped up to engineering again, and another woman. They get to Kerberos, and a few weeks into their mission the Galra resistance group who rescued Matt arrive, to check that the area is still free of the Galran Empire. Mrs Holt is so happy, but also, her son looks the same way he did when she last saw him 8 years ago, though more buff, scarred and tired. The sibling convinces them to let them come with them, and when Matt explains that Mr Holt is still out there Mrs Holt is like 'There is no way that you’re leaving me behind, the communications officer is like 'The government adopted me when I was 12, and they passed me off to the Garrison immediately, two years before they were legally allowed to so I don’t have much back there, I’ll come’. The Galra resistance group meets with the Blade of Marmora to form an alliance. They then meet with Voltron. The meeting is first with Allura, then the paladins of Voltron are introduced, minus Shiro because he’s missing. There are the obvious reunions.
Matt: What the f-
Mrs Holt: Language, Matt.
Matt: Mum, I’m fighting in a war and I was a slave for a year, let me swear.
Pidge: Who are you, you’re not the short beanpole I know.
Matt: As I was saying, MUM, what the heck’s a Pidge.
Pidge: I’m a Pidge. And Mum, you look a lot older than I remember.
Matt: KaTIE THAT’S NOT SOMETHING YOU SAY TO ANYONE.
Lance enters with a mug of coffee or something.
Hunk: Ah, I see you’re holding true to being the 20 minutes late with Starbucks meme.
Lance: Yes, but I woke up lat this morning and I have to uphold my beauty routine so I’m not sore-why is Pidge standing next to a hot Pidge what is happening am I okay.
Lance is barrelled over in a bear hug by his sibling.
Lance: *is confused*
Keith *is alarmed, the subject of his pining isn’t allowed to die*
Everyone else: *also alarmed*
Sibling: How dare you, not tell me or anyone else about Iverson being a dick to you! You were my role model! I came out as genderfluid to you before anyone else! Before I came out to Mama! You watched my debates and you went to everyone on of Freya’s hockey games, and you taught Maria how to use makeup when she was transitioning, and yet you couldn’t tell anyone of us, or even Mum or Mama about that!
Lance: Who-w-How do you know all that who are you?
Sibling: Well, you dense traffic light after that I thought it would have been obvious. I’m *name*
Lance: Um, no, *name* is 13.
Pidge: Lance…I can’t believe I forgot…We studied this…Time passes differently in space…
Lance: So you’re telling me that they’re, that you’re, my sibling? You’re, like, my age, if you aren’t older! How old even are you?
Sibling: I’m 19.
Lance: What the f-
Matt: If I’m not allowed to swear you don’t get you.
Sibling: You know what this means, right? Unless you were some sort of crazy party animal at the Garrison I got to drink before you.
Hunk: 19 is still underage though.
Sibling: In America maybe. But we live in Australia. So. Whenever I went home I got to drink. Because I was also at the Garrison from a program/branch thing in Australia I was bound by Australian rules so I was legally considered an adult and allowed to pilot the second Kerberos mission.
Matt: But more importantly. You think I’m hot? *bats lashes at Lance*
Sibling: Right, how could we forget about that beautiful gem.
Lance: How could you do this? Betrayed by my favourite little-what is is sibling? Sister?
Lance: How could I be betrayed by my favourite little sibling?
Sibling: Well first of all, I’m only your favourite until Freya or Maria is in the room and suddenly you’re not allowed to have favourites, and second, you may have been born before me but I’ve lived longer than you so I’m the older sibling now.
Lance: All around me are familiar faces, worn out places-
Allura: We are currently searching for our black paladin, Shiro, which is why we wanted meet with you, aside from solidifying an alliance.
Matt: Wait, you mean Shiro like Takashi Shirogane?
Keith: Yeah. He’s missing and we can’t form Voltron without him.
Matt: You must be Takashi’s emotionally constipated adopted child-I mean adoptive brother. But more importantly, he couldn’t even be here to meet me! My boyfriend’s such a *stares directly at Mrs Holt* goshdarned flake.
Pidge: *Snorts* And what a hecking shame that is! If you being here could have stopped him from going and cheesing disappearing then we wouldn’t be in this dang situation.
Holt siblings: *snorts devolving into cackles*
So that’s my au. There’s more. There’s so much more and I might draw some of it. I’m also considering a name/names for the sibling.
Or, alternatively the time passing differently in space could just be for langst.