Most of what we know about Plato is through his writing and that of his contemporaries. There is much conjecture surrounding Plato's date of birth, and even his name. Traditionally Plato was thought to be born around 428/7 BC, but some sources suggest he was born between 424 and 423 BC*. His parents were of Greek aristocracy. father, Ariston, and Messenia, his mother.
*There are at least a dozen recognised 'guestimates' for Plato's birth but I don't believe it to be vital information for the purpose here. Diogenes Laertius in his Lives and Opinions of Eminent Philosophers states Plato 'was born, according to some writers, in Aegina in the house of Phidiades the son of Thales'. One of his sources, the Universal History of Favorinus, infers Plato's family were sent by Athens to settle as colonists on the island of Aegina. They were expelled by the Spartans after Plato's birth.
It was tradition for the eldest son to be named after his grandfather. Although there is no conclusive evidence, it is widely speculated that Plato's grandfather was named Aristocles. The suggestion is that Plato's real name was Aristocles but there is nothing to say Plato was even the eldest son of the family. The doubts surrounding the name Plato is due to it being a common nickname, referring to stature. Plato means 'broad' and there is record of the name being given to boys long before 'Aristocles' was born. Diogenes Laertius states:
'And he learnt gymnastics under Ariston, the Argive wrestler. And from him he received the name of Plato on account of his robust figure, in place of his original name which was Aristocles, after his grandfather, as Alexander informs us in his Successions of Philosophers. But others affirm that he got the name Plato from the breadth of his style, or from the breadth of his forehead, as suggested by Neanthes'
Boys of Plato's social class were taught by Athens' finest educators. The curriculum would have featured the works of Cratylus, Pythagoras, and Parmenides. Plato's father died when he was young and he is thought to have two brothers and a sister but it is uncertain as to the order of birth. There was also a half-brother from when his mother remarried a politician named Pyrilampes.
The hostility was mutual, Plato described Diogenes as a 'Socrates gone mad'. Little evidence remains from Diogenes except some notable adages and some recorded 'unconventional' behaviour. Plato took up the philosophy behind this in The Republic. The more you delve into Plato's works the more you realise he was a reporter rather than an architect. Hailed as the originator of Dialectics it is likely he took the idea from Zenos, a pupil of Parmenides. Then there are the Dialogues, and what is termed his Socratic works.
The final piece of relevance we need concerning Plato, comes from after the death of Socrates. Plato travelled extensively throughout Greece, Italy, and most significantly, Egypt. Much information from before the Greek Dark Ages came from Egypt. There are theories that an anomaly with numeric systems that caused much Greek text to be exaggerated ten-fold. This is contentious although whatever the arguments for or against, it would make a lot of things more plausible. Such as the dimensions and time-frame of Atlantis, and ages of biblical characters.
Plato's last years were spent at the Academy and with his writing. The circumstances surrounding his death are hazy, it's almost certain he died in Athens around 348 BCE in his early 80's. Some suggest he died at a wedding, others believe he died in his sleep. Whether he is due all the credit or not, Plato has had a lasting impact on philosophy far beyond native Greece.
 Diogenes Laertius is known for his work 'Lives and Opinions of Eminent Philosophers' which professes to give an account of the lives of the Greek philosophers. It is an interesting insight into the lives of these famous Greeks. The work is written in the early 3rd century AD so it has some antiquity and ergo an empathic feel for the subjects. Montaigne stated he wished there had been a dozen of Laertius but others have a different view. One states:
"Diogenes has acquired an importance out of all proportion to his merits because the loss of many primary sources and of the earlier secondary compilations has accidentally left him the chief continuous source for the history of Greek philosophy" whilst Werner Jaeger referred to him as 'that great ignoramus'.
For my purpose the fact he is mostly criticised for being overly concerned with superficial details i.e. the lives of the philosophers, is of no consequence. They complain he lacked the intellectual capacity to explore their actual philosophical works but there is evidence much of his work may have been lost. My reason for giving credence to Laertius is the suggestion he was an Epicurean or a Skeptic. Typical of the ancient Skeptics, Laertius is impartial to all schools and it is for this reason as much as any other I tentatively tend to trust what he says.