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.
If by your statement about your father-in-law that he "announced (written form) his only daughter as a nominee for certificates and house" and by this you mean that he made a will to this effect and the daughter did not take possession of it when he was alive, then his announcement is considered as a will, and it is known that a will for an heir is Islamicly forbidden. After he died, this will cannot be applied unless all other heirs agree to it. In this case –which means if the heirs do not agree to approve of the will –and the man died leaving behind a daughter, a wife, four full brothers and two full sisters, a sister from the father’s side only as we understood, then his daughter gets half (of the inheritance) as Allaah Says (what means): {And if there is only one [daughter], for her is half.}[Quran 4:11] His wife gets one-eighth as Allaah Says (what means): {But if you leave a child, then for them [i.e. the wives] is an eighth of what you leave.}[Quran 4:12] The remaining of the inheritance should be divided between his full brothers and full sisters, the male twice the share of the female; Allaah Says (what means): {…if there are brothers and sisters, the male will have twice the share of the female. Allaah makes clear to you [His Law], lest you go astray. And Allaah is Knowing of all things.} [Quran 4:176]
On the other hand, the sister from the father’s side only has no share in the inheritance because she is prevented by the existence of full brothers and full sisters.
However, if by "announced (written form) his only daughter as a nominee for certificates and house" you mean that the father gifted the house and the certificates to the daughter during his life and before his death sickness, and she took possession of the gift and acted on it as the real owner, then this is a valid gift and the house has become the property of the daughter and it is not included in the inheritance.
Nonetheless, we did not understand what you mean by the National Defense Certificates and the National Saving Certificates. But if these are among the forbidden kinds of certificates, then the profit that comes thereof is not included in the inheritance. Rather, this is Riba (interest and/or usury) and it is forbidden. It is an obligation to get rid of it as it is not included in the inheritance. It is only the capital money that is included in the inheritance.
It should be noted that the matter of inheritance is very complex an issue, so a mere Fatwa which is an answer issued according to the question is not enough. Rather, the matter should be taken to an Islamic court to look into the case, or it should be presented orally (in person) to the scholars in case there are no Islamic courts. It might be that there is an heir who would not be known except after investigation, and there might also be a will, debts, or other dues that are not known to the heirs. It is known that these rights come in priority over the right of the heirs. Therefore, the inheritance should not be divided without resorting to an Islamic court, if any, in order to fulfil the interests of the dead and the live people.
Allaah Knows best.