Minecraft Java Process taking all available ram, destroys FPS

Hi, I have a server (1.16.5 ForeOptiFine) here where I play with like 7 friends, we all have no issues running minecraft with seus shaders and 1024x textures pack, except my brother. The game runs at 12 to 20 fps and when I see in task manager what's going on the Java process is using all the available ram (11 to 13gb). As soon as he hits "Enter Game" in tlauncher the ram goes to the roof and the process takes like all the ram it can get. My brother's specs are

- Motherboard: MSI mag z390 tomahawk

- CPU: Intel core i5 9400f

- GPU: Gigabyte AMD radeon rx 5600 xt rev. 2.0

- 2x8gb ddr4 ram

What I don't undestand is that my specs are worst than that and I have no problems. We already tried assinging more ram to java, assigning less, remove resource pack and shaders (this kinda solves the problem of FPS but the process still takes like 4gb to 7gb of ram), reinstalling windows, reinstalling JAVA ( we tried like 4 differente versions including JDK instead of just JRE). Even when we assigned just 4gb of ram to minecraft (through tlauncher settings) the process still takes 12gb of ram. We tried differente drivers for the gpu (older ones), we updated to the latests ones. I tried reducing chunks render distance to 2 chunks and that seemed to work a little bit (but is hard to play. like that) cause what is happening, I guess, is that the system starts swapping memory since all the ram is gone and new chunks are loaded into disk memory not ram. We don't understand why this is happening to him and no one else, spend 2 to 3 days searching the web to find a solution and couldn't find one. Please help us (sorry for my english, I'm from Argentina)

we reinstalled Windows and it didn't work ;____;

Quote from PluginsMaster

Try creating a backup and then generating a new world.

It happens in single player as well, is not related to the server or the world, we tried in single player and the rams usage goes to the roof =/

Quote from PluginsMaster

Do any of these articles help you?

https://support.microsoft.com/…2a36-964c-4d2e-8c93980d8a

https://west-games.com/minecraft-using-too-much-memory/

the first link is broken (404), the second one we already tried those things. It's so weird I don't understand why this happens only in his PC : (

Quote from PluginsMaster

Sorry, I wrote the first link wrong , but here it is:

https://support.microsoft.com/…36-964c-4d2e-8c93980d8a98

If it doesn’t work, try googling some more articles about it.

but the process taking all of the ram is Java process, not runtime borker =/ We've been googling for the past 3 days and couldn't find anything to fix that. Usually I don't post on forums because I find the solution somewhere but this time it seems imposible to fix T__T

Quote from PluginsMaster

The only thing thing I could think of is contacting Mojang (https://help.minecraft.net/hc/en-us/requests/new) or Windows support (https://www.microsoft.com/en-a…osoft-how-can-we-help-you).

thanks for the help