If you edit your tree online, please read the following article:How do I show one person in two locations in my online tree?
There may be cases where you want to create a relationship between two people who are already in the family tree. For example, if cousins who are already in your family tree are married to each other, you can attach them as spouses without listing any of them in the tree twice. You can also add a child, parent or spouse that already exists in the tree without having to add them again.
The Attach/Detach feature should be used in such a case. Attach, as opposed to Add, lets you draw a connecting line between two people who are already in the tree, and Detach removes that connection without deleting any of the individuals. For each type of relationship there is a way to Attach or Detach. For husband and wife this feature is located in the “Spouses” menu. For children it is located in the “Children” menu. For parents it is located in the “Parents” menu.
1. Right click on the person you need to attach to.
2. Select the menu which corresponds to the attach you need to perform. Parents, Spouses, Siblings, Children:
3. Select Attach:
4. Select the person to attach from the list: