When a man dies, the heritage goes, only, to the children, not the wife? Then, what went, wrongly, to the wife, 40 years ago, now, that she died, can the children consider that should be theirs, instead of their mother’s, the wife, because she shouldn’t have gotten it, in first place?
In a way you are right, however there are numerous rights that the wife has. She benefits and get supported from her late husband’s estate, until she remarries, as part of her ketuba. Aside from this you would also have to clarify if the husband left her a will, which might be like giving her this estate as a present before he died.
Another point, essentially the children inherit their mother, so the question shouldn’t really be applicable. Therefore, I am assuming that there are other factors and people involved here, and it isn’t possible to really say anything without also hearing the other side Therefore, I would advise that the whole situation be taken to a bais din to help verify what happened, and who has rights to what. There is a bais din in Sao Paulo, if you need help finding the bais din, let us know.