Hello! If you have created a wrong relationship between two people, you'll need to click on one of them first. On the left side of your screen, you'll see a few buttons ("Add partner/ex", "Add brother/sister" etc.), and below them "More Options".
If you click on this, you'll get more options (shocker, I know) - one of them being "Change partners". Choosing this allows you to change current partners into ex-partners or deleting the relationship altogether (as long as the couple doesn't have any children).
In addition (if one person isn't supposed to be on the tree at all), you could delete them under "More Options" -> "Delete [first name]".
Hope this helps!
