Good games for bad internet

30k like 30 kbps? Or 30.000 kbps?

If you're cool playing games that are probably older than you are, Fallout 1 is like 400MB and Fallout 2 is like 1GB at most. Both very good games that are still very fun, although difficult, with tons of gameplay hours you can sink in. Psychonauts is a little under 4GB I think, and it's amazing :D

Closer to ~10GB I could recommend Borderlands 1 & 2, Mass Effect 1 & 2, Fallout 3 & NV, etc.

Bunch of fun stuff less than 1gb in size. Some are older, some quite new. All should keep you busy for a while, covers plenty of genres.

Nuclear Throne
Mini Metro
Pacman Championship Edition DX
Orwell
Rogue Legacy
Shovel Knight
So Many Me
Steamworld Heist
La-Mulana
Into The Breach
FTL
Human Resource Machine & 7 Billion Humans
Full Bore
Freedom Planet
Fortix 2
Escape Goat
Devil Daggers

Command and Conquer franchise.
Sega Genesis Emulator

Banner Saga is quite good. From what I rmember invisible inc. and mark of ninja was also pretty small

Assault Cube is the answer. Latency won't be a problem with that game. Best game to have in a flash drive and take with you to anywhere. And the thing runs literally anything <10 years. And older too if it's still in good shape.

Maybe Zandronum works fine also. It's Doom 2 basically. I never used it though, so I can't tell :P

EDIT: Just downloaded AC. The servers are not as populated as they were used to be :(
Urban Terror should be fine too.

1990s era FPS games. I love the Descent series.

Probably PvE games (Killing Floor 2 PvE mode, Payday 2, etc)

If you'd like to play singleplayer games i can recommend Rimworld, Darkest Dungeon, Factorio, Botlike - a robot's rampage etc.

factorio, tropico 4 + 5, space run, terraria, legend of grimrock 1 + 2, jydge, the trine games, the older serious sam games.
newer fps are usually pretty huge to download.

From stuff that wasn't mentioned yet:

Ara Fell - 281MB
Cook, Serve, Delicious - 142MB
Duck Game - 250MB (honestly it's basically just a multiplayer game which might not be a very good experience with your connection, but there is local MP which you might have fun with if your brothers want to play with you or you have friends over)
Kero Blaster - 121MB
Momodora: Reverie Under The Moonlight - 173MB
Stardew Valley - 496MB
Space Pirates and Zombies - 157MB
X-COM: UFO Defense - 16MB (in case you're in the mood for retro; if you do choose to play it, I strongly recommend to use OpenXcom instead of DOSBox that the game comes with)

hero of the kingdom - millennium a new hope - Stardew Valley - quest for infamy

Wolfenstein 3d is like 8mb and offer a few hours of fun
Doom is small too and you can download a billion wad for it which is also quite insignificant in size.

Or pretty much any old dos games before 1995 will be less than 10 mb

Heroes of Might and Magic 3 is about 1-1.5 GB, pretty cheap on GOG (riidculously cheap on sales) and basically endless :D

I really suggest Battle for Wesnoth.

Goblin and Coins is like 15 Mb only and it will give you a few hours of fun and it's made by one of us.

You could always leave pc downloading for the night (nights?) ;)

Tactical Monsters Rumble Arena - it's even free so you can check it out

https://www.steamgifts.com/discussion/TpRDr/modern-games-that-run-on-a-potato-machine-small-gib-added-level-1-basic-sg-ended

This post could be helpful. It has mostly light games recommendations

64 kbps here, I can feel your pain

I was in a similar position when I first started playing on steam. I had 50kbps and it was slow af.
Broforce and Guacamelee are really fun and about 500mb download size. I used to downlaod bigger games at 50kbps but it took a lot of patience, downloading a few hours everyday. Took a few days to download anything around 7-10gbs.

The Binding of Isaac and The Binding of Isaac: Rebirth
Deep Dungeons of Doom
Chrono Trigger
Tomb of Tyrants
Death's Hangover
Transistor
Shadowrun Returns and other from this series
Hunie Pop
Plants vs Zombies
Undertale
Another World
Bastion
Wizorb
Gunpoint
Risk of Rain
Zombie Driver HD
Hotline Miami 1 and 2

They don't need to be multiplayer games, right? Bastion is really good, and it's less than 1gb. The original Deus Ex is one of the best games sci-fi shoorters out there, and let me tell you, the gameplay has aged really well, it doesn't feel old at all. And if you like RPGs, you could emulate Nintendo Ds games, or maybe even older games.

tbh all games that aren't tied to silly things like Denuvo and so on and could be played in off-line-mode.