Both 2 Peter and Jude are very similar as they both go over false teachings. We as the church should not allow compromise and to not allow false teachers and doctrine to enter. I also didn’t know that Jude was also Jesus’s brother.
Jude didn’t believe that Jesus was our savior until after the resurrection. I believe Jesus knew when His brother’s eyes would be opened that is why He mentioned who His mother and brothers were in (Matthew 12:46-50).