My theory!

Rajmata had another son, one that is older then Brijrat and he was married to Moniyas mom. But Brijraj wanted to be the heir or the king and so in order to do that he had to either kill his brother(king) or blame him for something bad and then get him killed (hence no mention of Rajamatas first son, because she may have disowned him before death).

After he got rid of his elder brother, like Iv seen in tellys sometimes brothers get married to the widow of the elder bros. He got married and in place became king and Komals husband. What he got to know after wedding is that Komal is pregnant with his elder bros kid, he told Komal to let this be between them and not let anyone know.Now just like in jungles a Lion never lets its predecessors cubs survive and would want his own kids to survive, when he got to know that Manyata will be heir and not one of his kids he thought to get rid of her. And I am assuming his plan to get rid of Manyata was heard by Murari who loved Manyata like his kid and then he saved her by kidnapping.

When the doc said lets let Manyata meet murari, Brijraj acted funny, so that got me thinking. So what do you people think?? Too far fetched??

I personally believe he's just moved on, and cannot accept that a daughter of his, with royal blood cannot show the type of pedigree which he expects from a Rajkumari (that blood should trumph an unbringing) in his eyes Moniya does not have the "tehzeeb" of royal princess, especially one of his blood: therefore he refuses to accept Moniya as Manyata as she currently is. Plus,I don't think he was too happy about shaking up the Uday- J alliance.

Oh well, we shall see.