Suppose...

Quite possible ..

I thought something similar ..He had a fling with Rajveer's mom but perhaps they didn't marry for some reason - maybe family not agreeing or whatever ..and then moved on with Anjana ..and then maybe at the time when adi was 16 ..this first lady blackmailed Harsh for money or something to look after rajveer claiming that he was his son (this is perhaps the ugly truth that pooja knew and which harsh had asked her to be shush about) ..so Harsh didn't really "cheat" on Anjana but he used to meet with this lady to support rajveer and give money or something ..and then finally perhaps that lady died (god knows maybe anjana psycho killed her too!) and then harsh stopped going to their place and Nani looked after rajveer .. and when rajveer grew up and became a CBI officer he tried to get back at the hoodas ..and now nani is completing what he started ...I vaguely remember in one of the epis harsh had felt that rajveer looked familiar but he couldn't place him .he was seeing him after 16 years so perhaps he didn't recognize him!!

I was thinking the exact same thing!!

What if Adi's memories were all messed up and Rajveer's mom was Harsh's first wife whom he left for his mistress Anjana.

The picture looked like a mother with her child (Rajveer) and she was wearing a mangalsutra

It would also follow the theme of EMA - Harsh cheating on his first wife and choosing his mistress in the end - which may have caused Rajveer's mother to commit suicide or something...we could even go as far as saying that perhaps Anjana killed Rajveer's mother so that Harsh would come back to her...maybe she made it look like both mother and child died...so Harsh would not be pulled by Rajveer and she would not have to take him into her home

Maybe that's why Anjana feels so protective about Adi - perhap's he was a witness who lost his memory to all this, or maybe he met this woman and Harsh wanted to take Adi into his home and raise Adi with his first wife and Rajveer...