The Mage Armor spell specifies that
you touch a willing creature
The spells do what they say, so Mage Armor works on a willing creature, with the singular article – a single objective.
That said, Mage Armor appears to be eligible for the Sorcerer's metamagic twin spell, which could cause him to focus on two creatures.
There's also no reason why you can not cast Mage Armor more than once on different targets, assuming you have the spell spaces available, since it's not concentration. However, you can not have multiple copies of Mage Armor that affect only one creature, or, rather, only one will have an effect.