Why do Both Tanjiro and his dad have the same scars?


I realized when I watched _Demon Slayer_ that both Tanjiro and his dad both
have scars on their foreheads, and I don't know if this applied to his dad,
but Tanjiro's scar is always changing shape and size.

Does Tanjiro's forehead scar have to do with anything about Tanjiro's dad
being able to use the fire god style? If you have any info on Tanjiro's scar,
I'd also like to know that.




Tanjiro told that, although the scar looked like a demon hunter mark, it
hadn't been one until he mastered the mark, as [wiki](https://kimetsu-no-
yaiba.fandom.com/wiki/Tanjiro_Kamado) summarizes it:

> He also has a scar on the top left of his forehead, which he received when
> he protected his younger brother from a falling brazier. The scar originally
> looked somewhat like a graze until his fight with the Hand Demon during the
> Final Selection, after which it develops into his Demon Slayer Mark.




Tanjiro told that, although the scar looked like a demon hunter mark, it
hadn't been one until he mastered the mark, as [wiki](https://kimetsu-no-
yaiba.fandom.com/wiki/Tanjiro_Kamado) summarizes it:

> He also has a scar on the top left of his forehead, which he received when
> he protected his younger brother from a falling brazier. The scar originally
> looked somewhat like a graze until his fight with the Hand Demon during the
> Final Selection, after which it develops into his Demon Slayer Mark.

