Duplicates in a family tree usually happen because:

• Someone was accidentally added to the tree more than once.
• People were connected by mistake, like attaching a sibling as a spouse instead of as a sibling.
• Relatives married each other.
• You're related to a set of siblings (or otherwise-related people) who married another set of siblings (or otherwise-related people).

To find out why people are showing up more than once in your tree and how to fix it:
 

Start by checking the list of all people

1. Go to your family tree.
2. In the toolbar on the left, click the Find button.
3. In the opened side panel, click on List of all people.
4. Look for duplicated names in your tree's list of all people. Or, enter a name and click Search.
   
   If someone's name is listed more than once, they’ve been added to the tree more than once, and all versions of them should be merged. If they appear only once, go to the next section.

If they appear only once on the list

If someone appears only once on the list, it means they were not added to the tree multiple times.

Other duplications happen when people have more than one role in a family tree. For example, if someone marries their cousin, they become  both a spouse and a cousin. The family tree shows them twice because of those different family roles, even though they were added only once to the tree. This can also cause other people related to them to appear multiple times in the tree.

If you know your tree has relatives who married each other (like a set of siblings who married another set of siblings), switch your tree to a horizontal view or (if you want to leave your tree in a vertical view) intentionally create a duplicate person to fix the issue. If you think something else is the problem, look for relationship mistakes within the tree.

Switch to the horizontal tree view

Duplicates caused by relationship mistakes, intra-familial marriages, or siblings marrying siblings will appear only when your tree is in the vertical view (with descendants and ancestors ascending vertically). To stop seeing these duplications, switch your tree to the horizontal tree view (with descendants and ancestors extending to the left and right).

From your tree, in the toolbar on the left, click the view button and select Horizontal. 

Find relationship mistakes

Usually, if you see duplicates in your tree due to relationship mistakes, you'll see multiple people duplicated. Follow the group of duplicated people up and down your tree until you find where the duplication ends. Check the couple at the end of the duplication for relationship mistakes.

Intentionally create a duplicate person

If people show up more than once in your family tree because of intra-familial marriages or relatives marrying each other, we can fix it by creating a duplicate of one of them. We'll disconnect a duplicated person from their parents (without deleting them), make a copy of that person, and then link them (the new version of that person) back to the parents you disconnected earlier. Your family tree view will be fixed, and you'll have the right relationship connections.
 

1. Go to your tree and click on the duplicated person.
2. In the opened card, click Profile.
3. In the top-right corner of their profile page, click Edit and then choose Edit Relationships.
4. Write down their parents' names and important dates (like birth and death).
5. Click the X next to each parent and then click Remove. This will disconnect them from the relationship but keep them in your tree's list of all people. Repeat for any additional parents.
6. Return to your tree, find, and click on one of the parents you just removed (for help, see Finding People in Your Tree). 
7. In the opened card, click Profile.
8. From the parent’s profile page, click Edit and choose Edit Relationships.
9. Choose Add Child.
10. Select Add new person.
11. Enter the information to create a duplicate person and click Save.