This varies between dynasties and of course not historically accurate as it is based on the novels I translated and read. So don’t bash me up if there are any misinformation or errors.

If there are any missing or incorrect information, kindly drop me a comment so I can make the changes accordingly.

Female Ranking in Families
Yuanpei Furen – Legitimate/legal wife that was first married (first official wife before all the rest)
Furen – Legitimate/legal wife
Guiqie – Concubine of higher status
Yiniang – Concubine
Tongfang – Lowest ranking concubine
Usually formal servants who was then ‘graced’ by the master. But a Tongfang is basically still a servant but have the privilege to sleep with the master.

Di Shu Ranking in Families
This Di Shu system is in place as a legal means to facilitate marriage and inheritance which works as an ranking/priority system. It does not mean that the oldest would get everything but the background/heritage of one’s mother will define what the kids would be entitled to.

In this system, one man was only allowed to have 1 official wife/Furen and this household is considered Zhengshi aka Official Family/Household. All the kids that the Furen gives birth to are considered as Di children (Di sons or Di daughter). They would be higher social status of that to other kids in the household or in society. The Di sons would be able to inherit titles, land and money when their father passes without interferences. In formal gatherings, usually only the Zhengshi would be allowed to attend. Even if the Di son is 5 years old and the Shu son is 20 years, the Shu son’s status would still be ranked before the Di son and would most likely not inherit anything.

The concubines that then man marries would be considered as Ceshi aka Side Household regardless if the concubine has a higher status or lowest. All the children from the concubines are considered to the Shu children.

Usually the more effort and money are spend on the Di children as they are the face of the entire household. Di daughters are expected to marry into other household as Furen and Di sons are expected to follow the father’s footsteps to be an official/scholar. Shu daughters of noble family sometimes do become Furen but usually to a lower ranking official household.

It is also possible for Shu children to become Di children. When their mother status in the family is promoted from concubine to Zhengshi, then all the Shu children that the concubine gave birth will be promoted to Di status. From the novels, usually the Di children would hang out together and would look down on the Shu children.

Read more at Wikipedia