Two or more than two persons are considered as a group (for the congregational prayers)
حَدَّثَنَا مُسَدَّدٌ، قَالَ حَدَّثَنَا يَزِيدُ بْنُ زُرَيْعٍ، قَالَ حَدَّثَنَا خَالِدٌ، عَنْ أَبِي قِلاَبَةَ، عَنْ مَالِكِ بْنِ الْحُوَيْرِثِ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " إِذَا حَضَرَتِ الصَّلاَةُ فَأَذِّنَا وَأَقِيمَا، ثُمَّ لِيَؤُمَّكُمَا أَكْبَرُكُمَا ".
Narrated Malik bin Huwairith: Prophet said (to two persons), "Whenever the prayer time becomes due, you should pronounce Adhan and then Iqama and the older of you should lead the prayer."