How do you get Two by Two in Minecraft?

Breed every breedable animal at least once - around 20 species including cows, sheep, pigs, chickens, wolves, cats, horses, donkeys, llamas, rabbits, turtles, axolotls, frogs, goats, camels, sniffers, armadillos and the rest. Mules do not count as separate (they come from horse + donkey), and yes, hoglins and striders count too.

What kind of advancement is Two by Two?

Two by Two is a Husbandry tab advancement in Java Edition, of challenge type, rewarding 100XP experience.

Two by Two

Tab: HusbandryChallengeReward: 100XPDifficulty: Hard

Quick answer: Breed all the animals!

Previous advancement: The Parrots and the Bats

How to get Two by Two

Breed every breedable animal at least once - around 20 species including cows, sheep, pigs, chickens, wolves, cats, horses, donkeys, llamas, rabbits, turtles, axolotls, frogs, goats, camels, sniffers, armadillos and the rest. Mules do not count as separate (they come from horse + donkey), and yes, hoglins and striders count too.
Most overworld farm animals are straightforward: pen two of each and feed them their food.
The rare ones plan around: turtles (seagrass, beaches), sniffers (torchflower seeds from archaeology, then breed two sniffers), axolotls (tropical fish buckets, lush caves), frogs (slimeballs), hoglins (crimson fungi, they attack you), and pandas/foxes/polar bears variants.
Nether animals need to be bred in the Nether: hoglins and striders (warped fungi).
Keep a checklist - the advancement does not tell you which species you are missing.

Tips

Start a breeding ranch near spawn and ship rare pairs home with leads and boats. Sniffers are the long pole: you need two eggs from brushing suspicious sand/gravel in warm ocean ruins and trail ruins, so check our archaeology guide.

More guides from this tab (Husbandry): Stay Hydrated!Bee Our Guest The Parrots and the Bats You've Got a Friend in Me Whatever Floats Your Goat!Best Friends Forever