In group assignments, you also have the option to allow intra-group peer reviews.
Peer reviews require a student to review an individual submission by another student. However, group assignment submissions are made by one group member on behalf of the entire group, and all group members have the same submission.
By default, the Allow intra-group peer reviews checkbox is not selected, which means Canvas will exclude members of the same group when assigning peer reviews. However, by selecting the checkbox, reviews can be assigned randomly to all members of the course, including members of the same group.
To allow Canvas to automatically assign a peer review to any student in any other group, including students from within the student’s own group, select the Allow intra-group peer review checkbox. Selecting the checkbox allows assignments to be truly random and disregard group associations.