I don't belive there is away to do this with stock (through settings). If you and your brother are on stock then your phone may have a hardware issue, or hes using an app to modify the values perhaps.
I know CM7 (alpha/beta/trial) ROM for the droid 3 does have options to modify haptic feedback values (via settings) check to see if hes on stock or CM7.
(A quick glance at the texting app should do it providing you dont use any 3rd party texting apps. Stock will have all the blue and what not and CM7 wont)