Vyom was Ranjan and Madhvi's biological son, but Akash is not. Its possible that maybe Akash is Vyom or another guy with similar appearance as Vyom. Can't be very sure about either as at times I feel Vyom is Akash because Akash sometimes acts very creepy especially with Shivani when she suggests him to kill her before he ever cheats on her and he completely agrees to the same.