Companion ages are given in the official Star Wars: The Old Republic Encyclopedia. What is not established is if the ages given are their age at the time you meet them, at the time they join you, or at the start of the game. Charles Boyd believes that the age in the encyclopedia is the companion's age at the time they are recruited as per a post in the thread on the current in-game year.

The three companions people seem to have an issue with are Kira, Nadia, and Mako. In the Encyclopedia their given ages are:

• Kira - 20
  
• Nadia - 22
  
• Mako - 19
  

Now, keep in mind that Mako is the Bounty Hunters first companion and Kira is recruited on Coruscant, so both come very early in the game, which means that by the end of the class story they have both aged 2~3 years, whereas Nadia is the last Consular companion to be recruited near the end of Chapter 3, so by the end of the class story Nadia has not aged much.

Could an argument be made that there is a student-teacher dynamic between some, or all, of these companions with the PC that some may find uncomfortable? Certainly. The relationship between the BH and Mako is more like partners. Whilst Mako is young, and likely learning from the more experienced BH, Mako is not a student. The relationship between the Knight and Kira is a bit more ambiguous as Kira does frequently refer to the Knight as "Master." But the Knight and Kira are likely about the same age and Kira becomes a Knight at the end of Chapter 1, so there goes that student-teacher dynamic. Now the Consular. That I can see as more problematic.

As already discussed, the Consular is most definitely Nadia's teacher (Master), and, based upon Senator Grell's will, also a ward in some capacity. Although, if you do the maths from when you meet Nadia in the beginning of Chapter 2 to when Nadia joins you as a companion near the end of Chapter 3, Nadia is ~20-21 when the Grell's board your ship and that puts Senator Grell's relationship with Nadia into a different light. In many ways Senator Grell infantilizes Nadia. Something I think is an issue in itself, and in part contributes to the idea that Nadia is younger than they are. Regardless of that, Nadia is most definitely the Consular's student (Padawan), and if you find the power disparity inherent in a student-teacher dynamic "icky" then a relationship between the Consular and Nadia is an absolute no-go.

One other factor is that there is no canonical age for the PC. This was intentionally left ambiguous and we are allowed to headcanon our character's age. In some cases it is implied that the PC is on the young side, I think most heavily so with regard to the Consular, but there is also room for the PC to be older, such as with the Smuggler who, at whatever age they are, already owns their own starship (although, who knows, maybe mummy and daddy purchased it for them), or the Trooper who is not a green private but an experienced sergeant who already had an impressive military career prior to being assigned to Havoc Squad. I do agree that the Consular voices, both male and female, do sound a bit too old.

For myself, my characters have a broad spectrum of ages. In my headcanon, my main, a Jedi Sage, was age 16 at the start of the story, which means they were younger than Nadia when Nadia become their Padawan. My Smuggler and Bounty Hunter, on the other hand, were both in their late 20's to early 30's at the start of the story. Also, do not forget that our characters spend five years in carbonite. As per the Smuggler story, one is in stasis when in carbonite, and if our character did not age during that time then they are now five years younger than they would be if not for that time in carbonite.

The game starts in 10 ATC (After Treaty of Coruscant); near the end of the year according to Charles. Each chapter in the class story is assumed to take approximately one year and the Battle of Ilum, which occurs right after the end of Chapter 3, is near the end of 13 ATC. Each expansion thereafter is assumed to occur in roughly real time. See the quote below for some more detail. That puts the current in-game year at 27 ATC, which means our characters have aged 17 years (12 years if they did not age when in carbonite). That means that Mako, who was 19 at the start of the game, is now 36 years old. That also means that if you headcanon your characters as 30~40 at the start of the game then they are now 47~57 (42~52 if you are not counting the years in cabonite).

The timeline according to Charles:

If you are interested in the stated ages for the other companions as given in the Encyclopedia see this post. Kiesu also advanced their age to coincide with the current in-game year, but I am uncertain of how they applied the printed age, whether that being their age at the start of the game or when recruited, so can not speak to the accuracy of the progressed age.

http://www.swtor.com/community/showpost.php?p=9852758&postcount=129

It doesn't seem that creepy to me.

 

Probably because of how I always interpreted the BH's own age. Keep in mind that the PC characters are supposed to be pretty young themselves. (Somewhere in the late teens to early twenties range.) And whereas Nadia is explicitly your student, Mako is more along the lines of being a partner.

It's not just her age. It's that she keeps telling the BH no. He keeps pressuring her until she has no-one left but him and finally caves.

The three companions people seem to have an issue with are Kira, Nadia, and Mako. In the Encyclopedia their given ages are:

• Kira - 20
  
• Nadia - 22
  
• Mako - 19
  

I've seen this list posted many times, but it is hardly canonical. It gives Talos Drellik as 27 for example. It is an obscure reference, from an obscure supplement put together by an intern or such.

What matters is how they're written - the narrative tropes that they clearly lean into - and how the voice actor portrays them. Nadia Grell is written and voice acted as a teenage girl, and leans into every 'teenage girl in Space' trope you can think of.

It's not just her age. It's that she keeps telling the BH no. He keeps pressuring her until she has no-one left but him and finally caves.

Also. There's no way in hell that the BH is in their early 20s.

I've seen this list posted many times, but it is hardly canonical. It gives Talos Drellik as 27 for example. It is an obscure reference, from an obscure supplement put together by an intern or such.

 

What matters is how they're written - the narrative tropes that they clearly lean into - and how the voice actor portrays them. Nadia Grell is written and voice acted as a teenage girl, and leans into every 'teenage girl in Space' trope you can think of.

Incorrect. The Encyclopedia was put together by the writers who wrote the class stories. Or are you claiming to have information that Charles Boyd, current Creative Director for the game and writer of the Trooper story, does not?

Oof… I’m actually not sure what everyone’s intent was when we put that together. There were numerous authors on the encyclopedia, and all class writers were consulted, but I forget if we made this specific distinction when presenting the information.

 

Giving it a quick look, I’m going to say that the companion ages in the encyclopedia are probably intended as their ages when they’re recruited, not at 13 ATC. For example, I don’t think Kira is intended to be younger than Nadia, but Nadia is listed in the encyclopedia as 22 while Kira is listed as 20.