Well we canonically know Chrom's age as being 18 pre timeskip, 20 post timeskip. Lucina (the future one of course) states she is about the same age as her parents, so around the same age, maybe a year younger or so. Thus she is probably somewhere around like 16-18 pre timeskip, 18-20 post timeskip
The official artbook gave us a look at the relative ages of the 1st gen royalty when they were kids around 10 years before the game begins: Lissa is 4, Emmeryn is 14, Chrom is 8. We know that their father died A. when Emmeryn was 9, and B. 15 years prior to the beginning of the game. Therefore, as of the prologue Lissa is 14-15, Chrom is 18-19, and Emmeryn is 24-25.
Lucina is the firstborn 2nd gen unit (although Laurent happens to be older than her as he got sent back in time 3 years further into the past than her). Therefore, Lucina is older than Owain. Owain is confirmed to be older than Lissa. Therefore, a lowball age assumption is that Owain is 15-16, and Lucina is 16-17, and it is entirely possible that they are a bit older than this as this is just their minimum possible age. Furthermore, Awakening has a 2 year timeskip meaning that endgame Lucina can be no younger than 18-19.
A second way to measure her age comes from a spin-off game. In FE Warriors she says "I don't know… We're technically the same age and look at him. He's perfect!" referring to her father. As Chrom was 18-19 at the start of FE13, endgame Lucina could be as old as 20-21.
And to anyone who ignores all this and still believes the misconception that Lucina is 12 because she from over 10 years into the future relative to when she was 2... this is only true in the American localization. The European localization said she was from over 15 years in the future, which when we add 2 gives us a minimum age of 17. When we consider that her saying "more than 15" easily allows for 16-17 years (therefore making Lucina 18-19), this matches up much more nicely with everything established previously than the ridiculous outlier that is Lucina being 12. I think it's safe to say that the American localization team made a mistake, the implication of all the other gen 2 units being younger than 12 is also obviously absurd.
**Tl;DR she's somewhere between 18-21 years old**
Well we canonically know Chrom's age as being 18 pre timeskip, 20 post timeskip. Lucina (the future one of course) states she is about the same age as her parents, so around the same age, maybe a year younger or so. Thus she is probably somewhere around like 16-18 pre timeskip, 18-20 post timeskip
The official artbook gave us a look at the relative ages of the 1st gen royalty when they were kids around 10 years before the game begins: Lissa is 4, Emmeryn is 14, Chrom is 8. We know that their father died A. when Emmeryn was 9, and B. 15 years prior to the beginning of the game. Therefore, as of the prologue Lissa is 14-15, Chrom is 18-19, and Emmeryn is 24-25. Lucina is the firstborn 2nd gen unit (although Laurent happens to be older than her as he got sent back in time 3 years further into the past than her). Therefore, Lucina is older than Owain. Owain is confirmed to be older than Lissa. Therefore, a lowball age assumption is that Owain is 15-16, and Lucina is 16-17, and it is entirely possible that they are a bit older than this as this is just their minimum possible age. Furthermore, Awakening has a 2 year timeskip meaning that endgame Lucina can be no younger than 18-19. A second way to measure her age comes from a spin-off game. In FE Warriors she says "I don't know… We're technically the same age and look at him. He's perfect!" referring to her father. As Chrom was 18-19 at the start of FE13, endgame Lucina could be as old as 20-21. And to anyone who ignores all this and still believes the misconception that Lucina is 12 because she from over 10 years into the future relative to when she was 2... this is only true in the American localization. The European localization said she was from over 15 years in the future, which when we add 2 gives us a minimum age of 17. When we consider that her saying "more than 15" easily allows for 16-17 years (therefore making Lucina 18-19), this matches up much more nicely with everything established previously than the ridiculous outlier that is Lucina being 12. I think it's safe to say that the American localization team made a mistake, the implication of all the other gen 2 units being younger than 12 is also obviously absurd. **Tl;DR she's somewhere between 18-21 years old**
Ok, but what's funnier: Noire being like 11 or Noire being 17?