The Geni Consistency Checker will report "Sibling too close" on any siblings where it is biologically improbable that they could be full siblings. Siblings born between 7 days and 245 days (about 8 months) apart will trigger this inconsistency. Siblings born within 7 days of each other will not trigger this inconsistency as these are considered twins.
This inconsistency is always considered a Warning
Auto-fix: There is no auto-fix for this inconsistency. One or more children may have the wrong birth date, or they may have the wrong parents, or in rare cases (such as premature births) this inconsistency should be marked correct.