Is there any harm to attach my sibling’s payoneer account to my fiverr?
No, it is against the Fiverr TOS to have more than 1 accounts on the same IP.
In your case, if you attach your siblings Payoneer to your Fiverr’s account then Fiverr detects that your account and sibling’s account having the same payment method. So, the Fiverr disabled all of your account even it is made up with different IP but due to same payment method Fiverr disabled your accounts.
So, my suggestion create a new payoneer for you.
My sibling doesn’t use fiverr. Neither does he use payoneer. I jsut created ion his name to get my payemnts since I don’t have an id card yet. Is it possible?
It’s best if you ask this question to fiverr customer support. This is too important to ask here. You may not get the correct answer. support.fiverr.com