Relative Clause Omission Rule

[vcolts]

Example sentences:

A lawyer is a person who works in the justice system and [who] represents people in court.

A lawyer is a person who works in the justice system and [who] does not have the power to sentence offenders.

A concubine is a woman who is a mistress and [who] does not have the same status as the official wife.

*Note: Please ignore the content of the sentences (I hastily put them together.).

Questions:

Is the "who" in red necessary? I see that sometimes "who" is repeated and sometimes not.

When would you say that I need to put it? I am assuming that it is a matter of clarity. Is it better to have it than not?

Thanks in advance.

[JohnParis]

[who] is not necessary in any of your sentences. They are quite clear without [who].

[vcolts]

I am kinda wondering about that as well.

Is the "who" necessary for the third sentence because the form of the verb in use is different?

[JohnParis]

In my opinion, I still believe that the second who in the third sentence is superfluous and stilted.
What are your comments on:
A concubine is a woman who is a mistress who does not have the same status as the official wife.