I don’t think so! The idea is that probably both Iruma and Ameri’s mom is from Japan~ So, probably, looks similar due to that reason alone! Chance are Ameri’s mom wrote Hatsukoi Memory~ so, this is big hint that Merize is Japanese just like Iruma~
With the whole romantic development between Ameri and Iruma, them being blood related is super low, because, if the plot changes to them being blood related, sorry, but, I gotta drop out of this series!
I love this series so much I bought all the books, so, they better not pull a sibling trope on me!

I see a resemblance in Ameri's mom and Iruma