Sultan - Sikki Step brothers?

After reading all the articles and views about Sultan's father... I think its not Mohan Kundra...I think its Kuku Bhatia, the father of Sultan.
We have seen his escapades in the show so i won't be surprised if he is the father and also when Sultan comes to know about this he will think to take revenge from Kuku by hurting RK as he dosen't know about Kuku being RK's step father...
What do you guys think?