The '''Cousins''' mod provides three modules which all include cousins and appear on the inner menu of the Relationships tab:
#'''Cousins''' lists all the cousins of an individual up to a predefined limit which is initially 4th cousin.
#'''All in-law marriages''' explores multiple marriages between two families, both siblings and cousins.
The second two of these searches can take quite a long time depending on the size of the tree. Therefore the search itself is restricted to administrators and the basic results are cached in the database so that anyone can see them. The table can be updated when it is necessary and it is also possible that they can be computed on a private computer and uploaded to the webserver. Caution: The computation uses temporary tables and these are usually not available for servers based on USB memory sticks.
400px|The start of a listing of Queen Victoria's cousins]]The first display shows for any person in the tree all their cousins, by default from first to fourth, if they have any. The number to display may be set to any number but increasing it to 7, 10 or more will inevitably take more time if at many generations exist in the tree. (Click on the picture to enlarge it.)
[[File:Victoria_relation_to_Charlotte.png|thumb|right|400px|Relationship with Victoria's oldest cousin]]
The name of the cousin is followed by brief defails of their life. Clicking on the cousin's name will show the relationship between the root person and the cousin including the ancestors through whom they are connected.
==All cousin marriages==[[File:all-cousin-marriages.png|thumb|right|
400px|The start of a listing of cousin marriages of European royalty]]
Occasional examples are found in many family trees of cousins or other close relatives marrying each other. Although marriages between first cousins are illegal in many US states, more distant cousin marriages are permitted and may be more common than people expect. This display collects all the examples in a tree together. The display puts the names of the husband and wife alongside the names of their common ancestors with dates and places of marriage. The list is sorted by the closeness of the relationship and the date of the marriage.
The number in the "Descent" column shows the number of generations from the common ancestor on the husband and wife's side resepectively. First cousins are thus represented as 2:2, second cousins 3:3 etc. The reason for this is that it is possible to go lower. The picture at the right shows examples of nephew-niece marriages (1:2). Brother-sister incest is represented as 1:1 and father daughter incest as 0:1. The example of Louis XIV and Marie-Therese of Spain shows an example of double first-cousin marriage. Where only one of the ancestors is shared, a footnote annotation (*) is added in the descent column and only the common ancestor is shown.
The relationship can be explored by clicking on the husband or wife's name which will always show their marriage first followed by their other relationships. Clicking on an ancestor shows instead a descendancy tree in which the cousin marriage will appear twice. This also works where there is only one common ancestor.
[[File:Victoria_relations_to_Albert.png|thumb|right|400px|Victoria's relations to her husband Albert]]
Most examples are not as close as these, and involve more distant cousins. So 2:3 (or 3:2) is a first cousin once removed, . They sometimes occur in clusters and to make these easier to spot, when names are repeated an occurrence number is added in square brackets after the name - ,  etc. These are actually links to a filter which will produce a separate report for the person concerned.
[[File:victoria-cousin-marriages.png|thumb|right|400px|Cousin marriages involving Queen Victoria]]
==All in-law marriages==
Sometimes two siblings in one family marry siblings or cousins in another family. This strengthens the ties between the two families more than a single marriage but does not in itself bring any genetic implications. It can include affinal marriages such as a man marrying his dead wife's sister, but most such marriages are not properly described as affinal and indeed there is no common name for this. They usually occur in pairs but sometimes happen in groups of three or more.
400px|In-law marriages in royal tree]]
This display shows all such marriages in a tree in groups ordered by date of marriage. The second line of each group shows the way in which the second marriage relates to the first using the codes "s" for sibling, "c" for cousin, "h" for half-sibling and "p" for same person. Thus one can have "s-s" where two siblings in one family marry siblings in the other family, "s-c" for siblings in one and cousins in the other, "c-c" where cousins in one marry cousins in the other, "h-s" where half-siblings in one marry siblings in the other and so on. If the same person marries two members of another family one can get "p-s", "p-c" etc.
Examples of all of these are shown in the royal example on the right. A repeated person is also marked with a number in square brackets. Thus Henry VIII is shown three times--not only were Ann Boleyn and Catherine Howard related, but Catherine of Aragon had previously been married to Henry VIII's brother.