Nyanaponika Thera
According to Buddhist texts, when a fully enlightened Buddha appears in the world, he always has a set of chief disciples. For the current Buddha, Gautama, his chief male disciples were Śāriputra and Maudgalyāyana, while his chief female disciples were Kṣemā and Utpalavarṇā. According to the "Buddhavaṃsa", all Buddhas of the past followed this pattern of selecting two chief male disciples and two chief female disciples. German Buddhist scholar and monk Nyanaponika Thera states that the reason Buddhas always select two chief disciples is to balance responsibilities according to each disciple's specific skills.