Responses
They adopted her. No surrogate !
Dojun didn't agree with the surrogacy, but instead they adopted a girl, and it was So-yi. That was shown in the side stories.
Thank you for the answers guys! <3
I have a random question maybe someone could answer for me. In the original Love is an Illusion I remember Si-wo's parents Dojun and Heesoo arguing about having a baby. Since Heesoo was a beta and couldn't get pregnant, didn't they talk about using a surrogate? And then had a debate about which one of their genes they would use? Did they ever reveal whose they used, or do we not know?
Also, side comment, I honestly kind of wished they made Byul and Si-wo's parents look just a tiny bit older. Even if Dojin and Hyesung "look young for their age" I feel like at least Dojun and Heesoo should look somehow different then. It just feels a little strange to me, as much as I love their appearances (and it feels more nostalgic to the original then), to have them look the same 17 years later, especially when they don't appear that much older than their kids!