Is it permissible for two brothers to perform 'Umrah on behalf of their deceased mother at the same time?

You both may perform two 'Umrahs for your mother at the same time, provided that each of you enters into a separate state of ihram for an 'Umrah, intending it on behalf of your mother. If a man deputizes two or more people for an obligatory act, then the obligation is fulfilled by the one who enters into ihram first, and the second becomes a supererogatory act. It is a condition that each of you must have first performed 'Umrah for yourselves before performing 'Umrah for your mother.