The early history of Rome is shrouded in mystery. No written sources survive from this early period and historians have long been forced to rely on documents written many centuries later. The tale these later sources tell is obviously not very reliable, but there have been long and detailed debates about how much of them we can believe.
Even if the Roman histories written in about 200bc or 100bc are taken at face value there are great chunks of the story of early Rome missing. Long years go by when nothing is recorded as having happened at all, which is obviously not what really happened. The later historians also include a lot of information about gods and monsters that is better read as being legend rather than history. This has caused some modern historians to doubt everything that these historians wrote and they declare that the early history of Rome is entirely invented and should be ignored. But such a sweeping statement cannot be true.
Ancient Roman writers such as Livy or Polybius had access to all sorts of historical sources that have since been lost. They could consult the official archives of Rome, which included such things as treaties with other states, the lists of men who had held official positions and financial accounts of the army, road building and other state departments. In addition to this the Pontifex Maximus, or Chief Priest, had the duty at the end of each year of writing down what he considered to have been the most important events. Those writings were then stored in the temples.
There were also numerous private documents, such as family archives, temple records and business contracts that could be consulted. None of these sources would have given a complete history, and many of them would have been biased - a family archive for instance would probably present ancestors in a flattering light. It is a matter of guesswork how reliable these documents were and how accurately the historians whose work has survived took information from them.
So with all those facts in mind we must turn to the history of Rome as we have it. According to the ancient historians, Rome was founded on 21st April 753BC by twin brothers named Romulus and Remus.
From "A Little Book of Ancient Rome" by Rupert Matthews.