On page 4 of Blood of Fiends (PZO9423, 2012), there's a sidebar that says Tieflings can be born from other humanoid races. This changes none of the game mechanics for your Tiefling, except size. If your humanoid heritage is not medium, your non-human Tiefling is the same size. There isn't an option in PCGen to change a Tiefling's size. (The rest would be flavor/description.)
The creatures of the depths of the Outer Planes do not limit their foul miscegenation to humanity. Elves, dwarves, halflings, and gnomes all have tales of tieflings in their histories, and those who appear among them now often suffer even greater stigma than those born to humans.
Other humanoids see tieflings in their midst as well. Many of the monstrous races of the world have demonic origins—most notably gnolls, who still thank the Mother of Monsters for their birth. Ogres, orcs, half-orcs, goblins, and other creatures that call upon the powers of the evil Outer Planes are equally likely to see tieflings living among them, but unless a given race holds to a code of racial purity, tieflings are far less likely to be shunned by such populations
It should be noted that while any monster or animal that breeds with a fiend may give birth to half-fiend offspring, only humanoids may give birth to tieflings. Thus, while it’s possible to encounter a half-fiend dragon, bear, or otyugh, any children of such creatures would be either half-fiends or normal members of their race. (And just as often, these less conventional half-fiends are simply sterile.) When discussing half-fiends and tieflings, it’s important to distinguish them from both true fiends (devils, demons, etc.) and simple fiendish creatures (creatures with the fiendish template, which are themselves denizens of the evil Outer Planes but similar in many ways to their Material Plane counterparts).
In game terms, the difference between non-human tieflings and human tieflings is purely a matter of size. Unless they have specific tiefling-related size modifiers, the tieflings of each of these races are the same size as their non-fiendish ancestors. They gain any of the bonuses or penalties related to that size, but gain no racial bonuses except those of the tiefling; beyond size, their humanoid ancestry is purely cosmetic."
Possible solution: An option to select your Tiefling's size.