Minecraft

tl;dr at the bottom.

You can't cross-play between Bedrock and Java. (Well...technically you can if you run a Java server and install the Geyser plugin onto it, but I get the impression you want a simple solution.)

Do we each need our own Minecraft account?

Yes. Two people cannot use the same Minecraft account in multiplayer at the same time.

Do we need to play on Realms or something like that?

Realms is basically a way to pay Mojang to run a server for you, rather than doing it yourself. Unlike a LAN game, or joining a friend's world in Bedrock, Realms and servers remain available to join even if the host player isn't playing.

sort of old school LAN style?

Both Java and Bedrock have ways to set this up. In Java, you can open a world up to LAN play. [https://minecraft.fandom.com/wiki/Tutorials/Setting_up_a_LAN_world](Tutorial for LAN play)

Both Java and Bedrock allow for multiplayer games over the internet. In Java, you can either use a Realm or set up a server on your own [https://minecraft.fandom.com/wiki/Tutorials/Setting_up_a_server](Tutorial for setting up a vanilla server). In Bedrock, you can join your Xbox friend's worlds so long as they are playing at the same time, and you can also join Realms or servers just like Java. (Sorry, I didn't see a tutorial on the Wiki for this)

One last thing, I'm a server owner who's been working with this stuff for the better part of a decade. If you want to chat more, I'm happy to help you.

tl;dr: Buy a second copy of Java edition and use that on the PC. Then you can host a LAN world from either the PC or Steam Deck. [https://minecraft.fandom.com/wiki/Tutorials/Setting_up_a_LAN_world](Tutorial for LAN play)

LOL I was like, I know about this, I can help! I play on Realms with my Nephews (but we're both on Bedrock) and then I read @[email protected]'s comment and yeah, you should go with their advice 🤣

The older Nephew and I prefer survival but my younger Nephew only plays creative so the kinda wonky solution we came up with is we'd start up a survival game and every now and then I'd say OK, we're going into creative mode and I'd switch over and let the younger nephew stock up on stacks upon stacks of their favourite blocks, spawn eggs, whatever they wanted then we'd switch back to survival. The two of us would go back to laboriously branch mining for precious diamonds and building a modest base out of cobble and oak planks while he would be building a mansion out of diamond blocks and sea-lanterns 😀

I think you both will need to be on Java version. You guys just playing vanilla? Setting up a server would make it so you both can connect to the world anytime, in case she plays when you are unavailable. Sounds like you don't need this. If you plan on having a separate world that you both play on together only, then you don't need a server; You can just open the world to LAN in settings (press esc) and she or you would connect to the other's local IP address. The person that is joining would connect from the title screen. This is just going off memory, I'm at work right now just killing time.

If I were doing this with my kid, I would have them play on their world, on their own account; They would just open to LAN when I had time to play, connecting with my own account.

Thanks everyone for the educational responses! My daughter and I are now happily playing in one of her bedrock worlds on LAN using the steam deck. Steam deck setup for the bedrock launcher was a bit tricky but now it runs awesomely, in game mode, and even has the exact same controller setup. If anyone is curious about how to set this up I'd be glad to help, I had lots of tricky missteps on the way, but I got there.

As for playing it on a SteamDeck, your best experience is going to be docked with a mouse/keyboard/external monitor. Minecraft Java does not natively have controller support.

If you don't have the setup to dock the Deck, you can install mods to add support for playing it using the Steam Decks controls. I will warn that playing that way is certainly not as nice as mouse/keyboard, but it is enough to still be fun. In fact, I have just written a guide for setting up the Steam Deck with Minecraft, in handheld mode, hopefully it helps if that's the route you choose to take.

https://sopuli.xyz/post/960903 << my guide

Bedrock edition and java edition are pretty much isolated from one another, unless you’re prepared to jump through numerous hoops. Best case scenario is to select one version.

Java edition is generally better, especially in terms of content (mods, shaders, skins, etc are all free and fairly easy to install). The only issue is that multiplayer is not the most intuitive. The easiest way to do this is to be on the same wifi network.

In a single player world, open the pause menu (escape) and in the options select “open to LAN.” Modify the world settings, then click create. Now your world will show up in the “multiplayer” section for other users on your network.

Minecraft has the ability to discover local network games, my daughter and I have played that way off and on for a while. We've played both on PCs, and one on PC one on phone without trouble. As long as the versions are compatible, they should be able to find the local game.

Edit to add a screenshot of the multiplayer screen, it's trying to find local games but there are none running currently :