Short answers, pulled from the story.
An Shigao was an early Buddhist missionary who settled in Luoyang in 148 CE and became the earliest known translator of Indian Buddhist texts into Chinese. He produced more than a dozen surviving works covering meditation, abhidharma, and Buddhist doctrine, making him a foundational figure in the transmission of Buddhism to China.
An Shigao is associated with the Parthian Empire through the An prefix in his name, which Chinese convention assigned to people from Anxi, China's name for Parthian territory. He has never been definitively identified with a named Parthian prince in non-Chinese sources; theories place his origins as far east as Margiana or link him to the Indo-Parthian kingdom.
Later Chinese catalogues attributed nearly two hundred translations to An Shigao, but scholar Erik Zurcher determined that only sixteen could be considered authentic. Stefano Zacchetti subsequently narrowed that figure to thirteen reliably attributable texts, with three of Zurcher's sixteen requiring further reconsideration.
Scholarly analysis of An Shigao's translations places them closest to the Sarvastivada school, one of the early Buddhist traditions. Whether he should also be considered a Mahayana follower is unresolved, though early Chinese sources call him a bodhisattva, a Mahayana designation, even though his corpus contains no Mahayana scriptures.
In 1999, Kajiura Susumu discovered two manuscripts in the Kongoji collection in Osaka Prefecture, Japan, containing four previously unknown texts. Three deal with meditation practices including anapanasmrti and the twelve gates; the fourth is a record of an oral commentary. All four have been proposed as potentially attributable to An Shigao based on their apparent antiquity.
An Xuan was a layman from Anxi who served as a disciple of An Shigao and also worked as a translator in Luoyang. Around 181 CE he collaborated with a Chinese scholar named Yan Fotiao to produce a Chinese translation of the Ugrapariprccha Sutra, a Mahayana scripture recorded in Chinese as the Fajing jing (Taisho 322).