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If this was an illegitimate child, did his parents have a relationship? Couple may not be sealed to each other if there was not a "marital" relationship Policy on sealing a deceased couple that were never married nor ever lived together.
On occasion, you may need to link a child in Family Tree to grandparents or other foster parents for sealings to be performed.
The child would need to be linked to all /any adult to whom they are getting sealed, and that relationship designated appropriately.
Yes. See here for policy: