If you have built your tree in the Online Immersive Tree:
Unfortunately, we do not yet have a method to enter complex relationships in an online family tree. We are working on adding this.
For the Family Tree Builder software:
The Attach/Detach feature should be used anytime 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.So 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 but 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.
There are multiple ways to reach these menus in order to invoke the Attach or Detach functionality. They are all the same so you can pick the one you find most convenient.
A) On the main menu, under Person -File/Edit/View/PERSON/Family/Charts.... You can reach the Spouses, Children or Parents menus.
B) By clicking on the EDIT button on an individual's genealogy card
C) By clicking on the EDIT button in the "Family" section.
I ve done it with FTB and it' works very well. Every person is connected as I want. But another question occurs: So I'm working with GEDCOM files that I import and/or export into FTB..And what happens with all my photo and pictures, all the tagg disapear and I have to redo all my work again..Have you one solution to keep all the works when changing the main tree online after importing GEDCOM?