am I getting this right

I think he might had more alpha siblings and this mc is one of them? I'm reading kiss me if you can but I don't remember anymore tbh

he has 6 siblings, 5 of them including a sister (who we will meet in a while if the author doesnt cut it off) are extreme alphas and one sibling who is an extreme omega.
Yes greyson is indeed the evil brother we see in chase's story but dont let it fool you, greyson is probably the second sanest sibling after chase who is normal by the Miller family standard

so mc in this story is the "dog brother" one from kiss me if you can story?

yes

6 siblings
Nathaniel miller - the eldest ( run away if you can )
Grayson miller and Stacy Miller( first daughter ) ( twins ) - Desire me if you can
Chase miller - Kiss me if you can
Larien miller - second daughter
Bliss Miller - Youngest ( Deflower me if you can )

Their parents - Ash and Koi - Lick me if you can
Their grandparents- Dominic and Juliet - Eat me up if you can ( most tragic and toxic story)

Desire me if you can ( Grayson and Dane )
This story is painstakingly beautiful and funny

thank youuu

Do all thease webtoons? or just novels?

They are all novels
So far we got adaptation for KMIYC and DMIYC

Thanks