Your family honor and devotion to your cause are your greatest strength and greatest weapon.
Prerequisites
Challenge class feature, smite evil class feature.
Benefit
Your levels in paladin and samurai stack for the purposes of determining the extra damage dealt by your smite evil ability.
Your paladin and samurai levels also stack for determining the save DC of your challenges and which challenges you have available.
Finally, if your combined total paladin and samurai levels reaches 20, you gain zeal based on your total combined level rather than only half (the same as if you reached Paladin 20 or Samurai 20).
You can multiclass freely between the paladin and samurai classes. You must still maintain your alignment and honor requirements to retain your class abilities and be able to progress your class level.