
Was he just deaf but can speak? Or he has both?

Through speech therapy the deaf can learn to speak by copying tongue and mouth positions, (and like feeling for how much air or pressure to put into certain sounds and whole lot of other complicated therapy stuff) but since they can’t hear the actual enunciation/sounds of words it isn’t always 100%, which is why he sometimes has misspelt speech bubbles (bubbles with an accent kinda)
Is Cecil and Pete siblings? Coz Cecil looks like grayson and her demeanor too.
Yes, they are siblings. They also have a baby sister, but didn't show her anymore hehe ٩(๑❛ᴗ❛๑)۶