Short answers, pulled from the story.
Asanga was a 4th-century Indian scholar regarded as the founder of the Yogachara school of Mahayana Buddhism. He and his half-brother Vasubandhu are considered the major classical Indian Sanskrit exponents of Mahayana Abhidharma and Vijnanavada, the doctrine that only awareness exists.
Some sources record Asanga's birthplace as Purushapura, the city now known as Peshawar in Pakistan, which was then part of the ancient kingdom of Gandhara. However, the historian Buton Rinchen Drub placed Asanga and his half-brother Vasubandhu in Central India, and the question remains unresolved by modern scholarship.
Asanga's magnum opus is the Mahayanasangraha, a systematic exposition of the major tenets of the Yogachara school arranged in ten chapters. It survives in one Tibetan translation and four Chinese translations.
According to traditional accounts, Maitreya Bodhisattva was the heavenly teacher who gave Asanga foundational instructions in Tushita Heaven. Scholars disagree on whether this Maitreya, sometimes called Maitreya-natha, was a historical human teacher as Frauwallner argued, or a tutelary deity encountered in meditation, as the 6th-century monk Sthiramati suggested.
According to Taranatha's History of Buddhism in India, Asanga founded 25 Mahayana monasteries across India. Among the most famed was Veluvana in the Magadha region of what is now Bihar, where he selected eight chosen disciples.
Vasubandhu was Asanga's half-brother, originally a monk in the Sarvastivada school. He is said to have converted to Mahayana Buddhism after meeting with Asanga and one of Asanga's disciples. Both are traditionally regarded as the principal classical Indian exponents of the Yogachara philosophical tradition.