After Yu Tieshan had announced his family background, Wang Cuihua had figured out the relationships.
If Suizi hadn't stopped her, she might have proclaimed their kinship right there and then.
The Yu Family's elders consisted of four brothers, who were named after the first four letters of the ancient Chinese phonetic alphabet: Jia, Yi, Bing, and Ding.
In Yu Shuisheng's generation, they adopted the character Shui (Water) in their names, so in Yu Jingting's generation, the character Tie (Iron) should have been claimed in their names.
Yu Jingting's original name was Tiegen (Iron Root), but since Suizi made fun of his name as a child, he secretly read a few books and changed his name to Jingting.
In such a manner, Wang Cuihua thought that Yu Tieshan's grandfather and Yu Jingting's grandfather would have been brothers.