Wuxia wife's naming scheme

[PJ]

Why is Guo Jing's wife known simply as Madam Guo,
while some people like Wu Santong's wife is known as Third Madam Wu, and Gui Xingshu's wife is known as Second Madam Gui?

[Tom]

Could it be because Wu Santong is the 3rd disciple of Yideng so his wife's name has a Third in it?

Gui Xinshu is the second disciple of Mu Renqing and his wife also has a Second in her name.

You see, it's kind of related.

[Felix]

Either that Wu is the third child in his family and Gui is the second. Unless these two were orphans that I do not know about.

Since Guo Jing is an only child, Huang Rong is referred to as Madam Guo.

[Felix]

Why is Guo Jing's wife known simply as Madam Guo,
while some people like Wu Santong's wife is known as Third Madam Wu, and Gui Xingshu's wife is known as Second Madam Gui?

Wait, was the wife of 6th Wu Tang disciple named Sixth Madam Yan?