Sullivan was diagnosed with a severe hearing loss as a child. With the assistance of hearing aids, he speaks and read lips fluently. He often expresses his personal challenges and journey in his work. Speaking to CineMovie about his movie "Cucuy," Sullivan explained:

"Amelia is hearing impaired and I'm hearing impaired. It was based on me... because I knew how it felt basically growing up and being teased and experiencing a lot of what she experiences. And I wanted to take that same theme and apply it to several of the characters that all sort of feel like outsiders in their own way."