First of all just because family members named in a Will pass away, does not invalidate a Will. If the only Will that can be found is from 1992, and that Will was properly executed, it is a valid Will and must be admitted to the Court. The house title cannot transfer without Probate either. If the 1992 Will states that surviving sons inherit, then all the sons take per the Will. No one has the right to live in the house, rent free, and the Executor named in the Will, has a duty to admit the Will to Probate. Whichever way the Will distributes property is how the Court will order the property distributed.
You as an interested party and beneficiary should seek a probate attorney in the County where your Mother lived at the time of her death immediately. Unfortunately, if you cannot find an updated Will, her intentions to disinherit will not be honored.
Please seek a consultation with an attorney, even if the 1992 Will was invalid the intestacy laws of Idaho would prevail in this situation. Intestacy is when you die without a will.
In Idaho the intestacy law states:
15-2-103. SHARE OF HEIRS OTHER THAN SURVIVING SPOUSE. The part of the
intestate estate not passing to the surviving spouse under section 15-2-102 of
this part, or the entire intestate estate if there is no surviving spouse,
passes as follows:
(a) To the issue of the decedent; if they are all of the same degree of
kinship to the decedent they take equally, but if of unequal degree, then
those of more remote degree take by representation;
(b) If there is no surviving issue, to his parent or parents equally;
(c) If there is no surviving issue or parent, to the issue of the parents
or either of them by representation;
(d) If there is no surviving issue, parent or issue of a parent, but the
decedent is survived by one (1) or more grandparents or issue of grandparents,
half of the estate passes to the paternal grandparents if both survive, or to
the surviving paternal grandparent, or to the issue of the paternal
grandparents if both are deceased, the issue taking equally if they are all of
the same degree of kinship to the decedent, but if of unequal degree those of
more remote degree take by representation; and the other half passes to the
maternal relatives in the same manner; but if there be no surviving
grandparent or issue of grandparents on either the paternal or the maternal
side, the entire estate passes to the relatives on the other side in the same
manner as the half.
So in your case, all surviving sons share in the Estate equally, with or without a Will. You have a 1/4 interest in the house, and belongings. It is to your benefit to seek legal help right away.