kiss me, liar or on this grayson will be always jerk huh. he's just scheming little b*tch

I read kiss me, liar ages ago, can you explain to me how these overlap? (=・ω・=) are they just in the same universe and acquaintances or are they like family?

Grayson is the seme's brother and the "best friend" of Keith, the seme of kiss me, liar.
This is probaly a couple of months before the uke of kiss me liar gets marked
Grayson knows all of the semes
Johs knows every omega
There are more books, the last book is about Grayson and Dane. That book takes place at the end of the extras of kiss me liar