If an adult child is a survivor of a deceased father who has a wife that does not want the children involved, does the adult child have any rights

Really need more details here.
I assume this is a step parent and what involvement are you talking about ?

If you are talking about inheritance, that depends on whether there is a will or not. If there is the terms of the will apply. If there isn't the local laws on inheritance apply. ANY question on law needs to include your general locale as laws vary by area.

if an adult child is a survivor of a deceased father who has a wife that does not want the children involved, does the adult child have any rights

If I understand what you are asking, the deceased father is survived by minor children and, in addition, an adult child. The children are in the custody of their mother, the deceased father's widow. Is this correct?

No, the adult child doesn't have any rights to visitation with his/her siblings (or half siblings, as the case may be).