Bottom Line
Families are strange. A person comes into your life and makes you feel like they had been here from the beginning. And some make you feel like a stranger even though you've spent years with them.
Raelle's presence was something similar to both Shui Koshing and Shui Xian. When did she manage to naturally find her place in their small family, even they both couldn't figure it out. Even his own daughter never made him feel this way as Raelle did. And the more he felt this way, the more Shui Koshing believed that it was the right decision to get her married to Shui Xian.
He didn't even realize when or how times passed while talking to Raelle and Shui Xian. He knew his son was becoming more talkative with her around. And Shui Koshing loved every single change in Shui Xian. No matter how small the change was, he knew it was enough to bring out his son from the abyss he had willingly jumped into back then.