Based on my reading of the form and your summary, section 10 would not need to be filled out because your father was survived by issue. (The natural children are "issue.") When you check the box in 10, it suggests that the children predeceased your father, which is not the case.
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It seems as though you may have misread the form as indicated by Mr. Frederick. Amend and resubmit.
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I concur with the other two answers. You should file a Supplement to correct the error. Language on the Judicial Council forms can be confusing.
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