I know keh yeh question 2007 ka hai, magar yeh aik interesting question hai, isliya iska answe da raha hoon.

Technically, jee haan, yeh baat rare hai magar possible hai keh pregnancy ka doraan  sex karna sai twins ho jaaian.Is phenomena ko Superfecundation kehta hain. Let me explain how:

Normally, her menstrual cycle ka doraan aik he egg mature ho kar release hota hai, aur aik he sperm usay fertilize karta hai, resulting in single pregnancy ( aik he baby hona).

Kabhee kabhaar aik say zyada ( 2)  eggs mature aur release hota hain, aur aik single intercourse say aana wale 2 sperms in 2 eggs ko fertilise karta hain, resulting in Fraternal Twins. Fraternal twins ki shakal aik doosra say nahin milti, aur un mein sai aik boy aur aik girl ho sakta hai.Magar important baat yeh hai keh yeh aik he  intercourse ka nateeja mein paida hota hain.

Is background ka saath ab aap kay question ke taraf chalta hain, keh agar female already pregnant ho to kya waqfa waqfa say intercourse karna say twin pregnancy ho sakti hai, and the answer is YES. Magar aisa sirf us waqt ho gaa, jab 2 eggs release hon ( like in fraternal twins), aur aik intercourse mein aik sperm aik egg ko fertilise kar kay pregnancy start kar day. Magar uska kuch hours ya 1-2 days ka baad dobaara intercourse kiya jaie, aur is intercourse say aana wala sperm pehla say mojood remaining egg ko fertilise kar day. Yeh bohot rare hota hai, magar possible hai, jisko Superfecundation kehta hain.

End mein, aik interesting baat bhee sun lein.Superfecundation ke wajah say Western culture mein aisa cases hoe hain keh aik woman ka pait mein  twins mojood  hain, magar each twin ka father different hai.

Interesting and surprising, but true.