Rob is a character we've wanted to introduce into the comic for quite some time now. He will play a much more prominent role in Peter & Whitney, but for now he just does what every big brother does: make snide comments about every aspect of his little sister's life.
On a side note, we've completely revamped both of our Patreons to now feature regular weekly updates every Friday with regular content starting on March 1st. Please consider pledging to get bonus content and support the series!