Doubling (forget trippling if you want to be realistic), but creating a binary system could work, but wouldn't give you as much additional distance as you might think.
Two roughly equal roughly sun like stars in a tight (say .5 AU or less) orbit around each other and a distant planet, somewhere between Mars & Jupiter distance - to extend the year.
Two sunlike stars doubles the luminosity, which means you can, using the inverse square rule, move the planet 1.414 times further away and it gets equal luminosity (but the interesting 2 star sky, which is always fun). Presumably that close, everything orbits on the same eliptic, but at different hemispheres, you'd get two sunsets most days. Kinda cool.
1.414 times further gives you an orbital period to the 3/2 power of that, or 2^(3/4) or 1.68 orbital periods, but you also have to adjust for twice the mass in the center, so, that speeds the orbit up by the square root of two.
Long story short, by adding a star, going from 1 sun like star to 2, keeping the luminosity the same, you've only increased the orbital period by the 4th root of 2, or about 19%. Your year is 19% longer.
3 stars becomes unstable for a planetary orbit within a few AU, so I won't even go there.
What you can do is give the planet a stronger greenhouse gas. That'll probably weaken the seasons, but you could move the planet considerably further away if it has a thicker atmosphere with more CO2 and/or Methane or water vapor. You could perhaps even double the distance using the right atmosphere which would make the year 2.828 times longer, add your 19% increase to that and you get 3.36 earth years.
12 Earth years is too difficult to explain unless you go for more massive, hotter, more bluish stars, which have shorter lifespans.
If you have two stars each with 1.5 solar masses their luminosity grows by the 4th power of that or about 5 times. The inverse square rule means, 2.25 times the distance and 3.375 times the orbital period. Now you're getting closer, but 1.5 solar mass stars have shorter lifespans, about 3 billion years.
Adjust accordingly, but 1.19 multiple for 2 stars, 3.37 multiple for 1.5 solar mass per star, maybe as much as double if you give the planet a strong greenhouse gas.
1.19 x 3.37 x 2 = 8 year orbital period. That's about as far as I'd be comfortable pushing it.