You got two choices. You can have two brothers that died and got to reincarnate as the Weasley Twins or the MC could have died in his world and was reborn as Ronald Weasley.
If you decide to do the twins, then embrace their personality and also become pranksters because it would make the fanfic better.
Things to point out
1. You will not have a lot of freedom since I doubt Molly will let their son/s practice magic at an early age so you will have to be discreet about it.
2. Weasley's are poor so I doubt they will have any amazing books on magic like on Occulemency and Legilimency.
3. No house elf, they cant afford one so you can just have one.