Two or more than two persons are considered as a group (for the congregational prayers)

Narrated Malik bin Huwairith:

Prophet ﷺ 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."

حَدَّثَنَا مُسَدَّدٌ، قَالَ حَدَّثَنَا يَزِيدُ بْنُ زُرَيْعٍ، قَالَ حَدَّثَنَا خَالِدٌ، عَنْ أَبِي قِلاَبَةَ، عَنْ مَالِكِ بْنِ الْحُوَيْرِثِ، عَنِ النَّبِيِّ ﷺ قَالَ " إِذَا حَضَرَتِ الصَّلاَةُ فَأَذِّنَا وَأَقِيمَا، ثُمَّ لِيَؤُمَّكُمَا أَكْبَرُكُمَا ".