Fatal Error for new posts and post previews

Fatal error: Cannot redeclare post_templates_plugin_init() (previously declared in /home/a2981/public_html/wp-content/themes/gameaddict/post_templates.php:116) in /home/a2981/public_html/wp-content/themes/gameaddict-child/post_templates.php on line 117

I don’t have a clue as to why this may be happening. Any assistance would be appreciated. I can follow instructions pretty well so if you want me to try multiple solutions I do have admin access, filezilla, and notepad++ at my disposal.