As-Salāmu `Alaykum , My cousin's wife died few months ago in New York, she had a son & a doughter, my cousin was with her all the time & still loves her. Now his wife's parents wants share from her belongings (Jewelery, diamond & from her bank savings).
please provive fatwa in this respect.
Jazak Allah Khair

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

The parents of the woman whom you referred to in your question have the right to ask for their share in the inheritance of their daughter as Allaah prescribed a share for them in her inheritance. Since she had left direct heirs who are her children, her father is entitled to one-sixth from her inheritance, and her mother is also entitled to the same share as her father; Allaah Says (what means): {And for one’s parents, to each one of them is a sixth of his estate if he left children.}[Quran 4:11] Her husband is entitled to one-fourth of the inheritance due to the existence of the children (who are the direct heirs); Allaah Says (what means): {But if they have a child, for you is one fourth of what they leave, after any bequest they [may have] made or debt.}[Quran 4:12] The remainder is for her son and her daughter, the male twice the share of the female; Allaah Says (what means): {Allaah instructs you concerning your children [i.e. their portions of inheritance]: for the male, what is equal to the share of two females.}[Quran 4:11]  

Therefore, the inheritance of the dead woman – her money, jewelry and all what she possesses – should be divided into 36 shares, her husband gets one-fourth of it, which is 9 shares, her father gets one-sixth, which is 6 shares, her mother also gets one-sixth which is 6 shares, her son gets 10 shares, and her daughter gets 5 shares.

The husband of the dead woman should fear Allaah and give her father and mother their right from the inheritance because Allaah threatened whoever goes against His Limits concerning the division of inheritance as He Says (what means): {And whoever disobeys Allaah and His Messenger and transgresses His limits- He will put him into the Fire to abide eternally therein, and he will have a humiliating punishment.}[Quran 4:14]

The fact that he loves her and did not separate from her is not a sound reason to prevent her parents (from the inheritance), and was the issue a matter of love and care, then all her inheritance would be for her parents and the husband would not have a share in it, because the parents love their children more than anyone else, and they are the ones who brought her up (when she was small) and took care of her more than her husband ever did.