life insurance passes outside of probate so the fact there is a probate action on the fathers estate means nothing. The benefits of the policy are now part of the son's estate.
any asset of the son's not disposed by a will will be distributed per the laws of intestate succession of his state of residency.
this is the basic rule of distribution of Wisconsin:
Everything to the spouse (but see the exceptions below)
If there is no spouse, everything to the issue per stirpes. Issue means direct descendants including children, grandchildren etc. Per stirpes means that everything goes to the children if they are all living, with nothing to the grandchildren. But if Child #1 of the Decedent has passed away, the children of Child #1 (the grandchildren of Decedent) get to split Child #1’s share.
If no spouse or issue, everything goes to the parents.
If no spouse, issue or parent, then to the siblings or their issue per stirpes.
If no spouse, issue or parent or issue of parent, to the grandparents or their issue per stirpes, one half on the mother’s side and one half on the father’s side.
If there is no person described above, then the Wisconsin School Fund gets the property.