Boku no Kokoro no Yabai Yatsu - Vol. 13 Ch. 175.1 - Vol.13 Extra

[MangaDex]

 

[arun2017]

So is she like his half sister or stepsister

 

[LemonLies]

So is she like his half sister or stepsister

Seems like half-sister since his mom's partner's other children are mentioned separately

 

[Aimr]

Mama Yamada is older than papa

 

[xyzzy]

My brain shorting out trying to calculate all the ages

 

[Psychronia]

Who's Yamada Kirara?

 

[the_legendary_klobb]

Who's Yamada Kirara?

Anna's aunt, her dad's half sister

 

[NagoyaR]

First child at 17 and one at 45! What a range!

 

[JagdPanther]

So, contrary to one of the comments in the main chapter thread, the grandfather is self-made, so Yamamom didn't necessarily grow up rich, at least early on.