Fastoche automatically detects which children are related by their parents. If they have at least one shared parent, they will appear as siblings. However, if there are duplicate parents, the link will not be made.
Duplicate parents can be merged using the Merge Parents Tool, under Tools. After reviewing the summary of information for each duplicate, select your primary, make sure the other duplicates you wish to merge with that primary are checked. Once you have made all of your selections select the Merge button at the bottom of your screen. You can merge as many parents as you wish at one time by expanding and making your selections under each duplicate listed.
If you see a red bar in a parent's profile that says, “Duplicates”, that means this person has a double. If you select that bar you will be taken to the Merge Parent Tool, but only that parent will be listed. To merge parents in bulk, go directly to the Merge Parent Tool listed under tools.