Talking with parents who have three kids, or kids from larger families, I've learned that, on average, having three kids takes you through the looking glass. Packing kids on top of that number adds to the workload, but at least you remain in that same altered reality you entered with number three (and no, I'm not willing to test this hypothesis).
With two kids, at least in a two-parent household, the tables are leveled. Even if there's the rare total meltdown with both kids, there are two supposedly older and wiser adults who can step in , one per child. With just one parent on call, it's still relatively manageable. 95% of the time, one child will lose it, but the other one will be stable enough to set aside while you wrangle the troublemaker. For instance, in the pic below, we all know that this sweetness will quickly end with one child running off, tripping, or pushing the other into a pole. That will generally leave one child needing assistance, and the other laughing or nursing a grudge.
With two kids I often thought of parenting as an "us vs. them" kind of arrangement. A very loving one, naturally, but still, I thought, "I'm the dad and I'm going to maintain control. You're the kids, and I'll eventually get my way." But now, with three kids, I'm beginning to realize how ridiculous this is. It's like facing a power play in hockey, but for the whole game. You're constantly a man down. As such, "winning" isn't the end goal. Survival - that's the strategy.
Thankfully, three kids can play well together, especially when the first two monsters absolutely adore the baby.