I assume, based on your wording, that the two you already have are twins? I am in a similar situation. Twins first, and the third is younger. Mine are closer in age than yours; my twins are now 6 and the younger is 4. My experience was that the third was way more work than I was prepared for. Everyone always said oh, twins, that must be so much work, you must be exhausted, etc. The reality was the twins were ok to manage because that’s all we knew at the time. When our life got insane was when we added the third at a different developmental stage.

I don’t know that I have any great LPTs for you, except be forgiving of yourself, your partner, and your older two. Things will be hard and you will all do, say, and think things that you don’t mean. It’s ok. The laundry/cleaning/etc will get done, eventually. You will all be tired. You will cry. You will question your sanity and your ability to handle this. It’s ok. Lean on whatever support system you have in place and absolutely do not feel bad about asking for help! Show all your kids that you genuinely love them and care about them and everything else will take care of itself. Best of luck!