Can my brother and I open these Fiverr accounts together in two browsers on my PC and work?
Fiverr goes by your IP address, so using different browsers will not fool them.
If you and your brother both want to freelance on Fiverr you cannot offer the same services. Also you need to contact CS to get there permission or you risk losing both accounts.
please don’t do that. fiverr don’t allow to create two account for a person or within a single ip address. so avoid this method