Short answers, pulled from the story.
Philostratus the Younger was a Greek sophist of the Roman imperial period who flourished in the third century AD. He is also known as Philostratus of Lemnos and is the author of a second series of texts called the Imagines, which does not survive in complete form.
Philostratus the Younger wrote a second series of Imagines, a work involving descriptions of artworks. It is the only known activity of this author, and it does not survive completely.
Philostratus the Younger's mother's father is identified as Philostratus of Lemnos, who was the son-in-law of the famous sophist Philostratus of Athens. This makes Philostratus of Athens the great-grandfather by marriage of Philostratus the Younger.
The dating of the Imagines varies between 250 and 300 AD. If the earlier date is correct, the author may be the same Philostratus who served as archon of Athens in 255 AD.
He may have been. Scholars note that if the Imagines was written closer to 250 AD, the author could be identified with a Philostratus who held the archonship of Athens in 255 AD. The identification remains unconfirmed.
Arthur Fairbanks produced an English translation of the Imagines. His edition, published by William Heinemann and G. P. Putnam's Sons in 1931, covers pages 281-368 of the Philostratus volume.