Why are there quasars that are exactly the same (like twins) . . . ?
Where did you read that? They could be similar according to our limited observation, but same, as in identical, would seem unlikely.
When radio telescopes were first turned on the heavens, point sources of radio waves were discovered (along with spread-out regions of emission along our Milky Way). Astronomers using ordinary visible-light telescopes turned toward these radio points and looked to see what was there. In some cases a supernova remnant was found, in others, a large star-birth region, in others a distant galaxy. But in some places where point sources of radio waves were found, no visible source other than a stellar-looking object was found (it looked like a point of like --- like a star does). These objects were called the "qausi-stellar radio sources", or "quasars" for short. Later, it was found these sources could not be stars in our galaxy, but must be very far away --- as far as any of the distant galaxies seen. We now think these objects are the very bright centers of some distant galaxies, where some sort of energetic action is occurring, most probably due to the presence of a supermassive black hole at the center of that galaxy (supermassive = made up from a mass of about a billion solar masses).
 from
Frequently Ask Questions's About Quasars, compiled by Dr. John Simonetti of the Department of Physics at Virginia Tech.
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