Each of the Cahill family branch has its own crest or logo that symbolizes something about their branch. They can use their crests to leave a message to their other fellow branch members, or they can use it to scare other Cahills from a different branch (such as the Madrigals, who leave a "M" to scare other Cahills away).
Lucian BranchThe Lucian crest has been modified over the years, but its central image, the double-headed snake, has remained unchanged. Like the often used personificative qualities snakes, it is symbolic of Lucians traits such as cunning and deceptiveness. The simpler Lucian crest consists of the same shield pattern, losing the scroll, and the snake is reduced to one snake-head. The Lucians are known for their art of poison. Ian Kabra and Natalie Kabra are the current Lucians.
Ekaterina BranchThe Ekaterina branch's symbol is the dragon, The dragon is a mythical creature that appears in many forms, so it symbolizes the Ekat's creativity, inventiveness, intelligence, and willingness to destroy everything that is in its way. Also, in 'Vespers Rising,' Katherine replied that her favorite animal was a dragon and in response to a comment by Gideon about how they aren't real she, replied, "maybe I'll make one." She is seen in the same book carving a dragon into the dining table.
Note: This event also shows that Ekaterinas should be creative as well as Janus (it is a known idea that the qualities that makes a good scientist include creativity and curiosity), although the Janus are more based on creativity while Ekaterinas pride themselves mainly on organized intelligence. Alistair Oh is the current Ekaterina leader
Tomas BranchThe symbol of the Tomas branch is the polar bear, a creature that has a fearsome reputation but rarely attacks unprovoked. The Tomas consider themselves similar to it, for they prefer to use their strength on the playing field more than on the battlefield. Hamilton Holt and the Holt Family are the current Tomas.
Janus BranchThe Janus's symbol is the wolf. It symbolizes the Janus's elegance and wisdom, creativity, and large imagination. But, it also means that they can be deadly when it is neccessary. Jonah Wizard is the current Janus.
Madrigal BranchThe Madrigals use the Cahill "C" to symbolize their hope to reunite all of the branches of the Cahill Family. They also use the Madrigal "M" in order to send a message of fear. Unlike the other branches, the Madrigals do not use an animal on their crest or a regular crest. Also notable is that there is no "official" smaller crest for the Madrigals. Amy Cahill and Dan Cahill are the current Madrigals. For more information, see the Madrigal Branch page.