Complex sentence: He is the comic relief of the group (seeing as he is always making mistakes with comical results), while not an antagonist in the series, his selfish antics are often the cause of many of the misfortunes that befall the group.
Split into simpler sentences: He is the comic relief of the group being that he is always making mistakes with comical results. While not an antagonist in the series, his selfish antics are often the cause of many of the misfortunes that befall the group.