When there are three persons, one of them should lead them. The one among them most worthy to act as Imam is one who is best versed in the Qur'an.
قَالَ رَسُولُ اللَّهِ ﷺ إِذَا كَانُوا ثَلاَثَةً فَلْيَؤُمَّهُمْ أَحَدُهُمْ وَأَحَقُّهُمْ بِالإِمَامَةِ أَقْرَؤُهُمْ