usually by carried out by counting the maximum amount of repetition that you and your brother could done over a fixed amount of time (lets say about 1 minute), the one with more repetitions is more likely to have muscle endurance.
The absolute method is done, normally, carrying out by calculating the maximum amount of recital that you and your brother could do over an allotted amount of time. For example, in about 1 minute, the person with the alternative recital is more likely the one with more muscle endurance.
