"There were other people to weigh in on their fight."
"There were people weighing in on their fight."
"There were other people to weigh in on their fight."
"there were ~" 「〜もいた」
"other people" 「他人」・「他の人」
"to weight in on ~" 「〜を仲裁する」
"their fight" 「彼らの喧嘩」
"fight" 「喧嘩」"argument" や quarrel" なども使えます。
"There were people weighing in on their fight."
"there were people ~" 「〜人もいた」
"weighing in on ~" 「〜を仲裁している」
[仲裁する](https://eikaiwa.dmm.com/uknow/questions/46432/)についてもっと詳しく知りたい方はクリックしてください。