Pyo Yoontae does infact know that mc is his childhood love. The reason he hasnt brought it up is because he noticed mc is hiding it and doesnt want mc to avoid him (in the novel we get a bit of his perspective and we see that hes anxious and scared but would accept it if mc didnt want to be with him)
Another fun fact is that in this specific stories omegaverse. Your most  significant/important moment can influence the smell of your pheromones. And bc pyo yoontaes most most significant moment was the time where he played with mc in the winter, his pheromones smell like that too!
And lastly if I remembered correctly, in the novel ml mentioned wanting 5 kids! Psa this one I'm not too sure if it was exactly 5 kids because my memory is a bit hazy but yeah. Hope you enjoyed my yap Lol