no they knew tht they were mother and son, after prerna and anurag gets divorced, sneha gets bone marrow but to save her anurag and prerna have another child prem, but tht prerna was with bajaj, and sneha was saved after prem was kidnapped by komolika, and apo*na kidnapped him from her and he was raised by her and was named yudi then, after the 20yr leap, he comes back and he then finds out tht prerna is his mother, but apo*na tells him tht he is illegitimate and they abandoned him to hide their extra marital affair and prem believes tht, and he creates lots of problems, and when prerna goes to jail, he takes away bajaj's property and bajaj leaves and nobody knows where he is, so when prerna comes back, she gets to know all this and declares war against prem, and now only prem realised tht his parents r good and he was never abandoned but was kidnapped from them.
i hope tht helps, sorry if i confused u even more.