A junior high reading comprehension level would probably be best, although I'm willing to consider things more juvenile or advanced. It can be a paper and ink graphic novel or a digital format like a web comic; either is fine.
You might want to give it a read yourself before reading it with your kids, though, to make sure you think it's appropriate. But personally I could see myself introducing it to my kid when they turned like.... 10 or 11 probably, if/when I have one. It should be noted the woman is telling her story from the ages of 6 to 14 in the first book, so she had no choice but to be exposed to these things at a very young age.
[1] https://www.amazon.com/Logicomix-search-truth-Apostolos-Doxi...
The comics involve mice from different cultural backgrounds (fishing villages compared to inland towns, same language but different dialects), there are some female characters (Sadie, and Gwendolyn is the leader), and a mix of ages, from young hothead to wise greyfur. Some libraries carry these books in physical and electronic format.
https://www.simonandschuster.co.uk/books/Victor-LaValles-Des...
There's a light novel series by the name of Spice and Wolf. It's fully translated in English. It's about a trader, a wolf goddess, and their adventures in capitalism-related escapades as they make their way across medieval Europe.
Both of them also have anime adaptations that are close to its source material in case your kids get bored (although Spice and Wolf's is incomplete).
And, while it's not a comic book, Anthem is a novella by Ayn Rand that depicts a world set in the future without the word "I" and how , in spite of this, one man rediscovers individuality.
The subject matter for all three of these works is thought-provoking enough and appropriately challenging for 13 year-olds