If you are speaking of the relative or relatives entitled to share in your property if you die intestate (without a will) then if you are unmarried your parents are your next of kin. If they were deceased then your sister would be your next of kin.
In another sense they are all your next of kin. See related question link.
Generally, when a father dies his wife and children are his next of kin. However, in some states his wife inherits everything. If there is no surviving spouse then his child(ren) is next-of-kin. You need to check your state laws of intestacy. You can check out your state at the related question link below.
Mother, if you mean wife of the deceased husband.
The mother or father or legal guardian of the sisters. if there is no guardian the sister is next of kin.
Typically the state foster care system.
If a man dies and is survived by his father and sister, the father would likely inherit the man's assets as a direct blood relative. In the absence of a will specifying otherwise, the father would typically be the primary heir according to intestate succession laws.
My Mother and Father's anniversary is next Friday.
The child's father. If the father is not available, a brother or sister over the age of 18 can act as next of kin in most states. Lacking a viable guardian, the court may appoint one.
THe Father
Without a will of intent all inheritance will go to the next of kin. The order of that is wife, father/mother, son and daughter.
Your mother, but both parents are next of kin
The next of kin is usually a child and not a sister. For example, if a mother passes away, the next of kin would be her husband and then her children.
Your adult children.
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