Marco's dad is Peter, who lost interest in life for two years after the supposed death of Marco's mother, Eva. In reality, she was infested by Visser One roughly a year and a half prior to the series, and her death in a boating accident was faked as a way to get her off the planet. Throughout most of the series, Marco battles with himself about her fate, debating whether he should he kill her or try to set her free. He comes very close to killing her in several books, until he finally frees her in The Revelation. Marco's father was uninformed about the true whereabouts and status of his wife until that same book, when he is finally told the truth and is the first of the Animorphs' relatives to join the war effort.
Marco is reluctant to fight because he knows that his father would be devastated by his death. He also argues that they are simply kids and that this is not their battle. When he coins the phrase "Animorphs", he describes the group as "idiot teenagers with a death wish." However, he also has a strong sense of loyalty, and says that he will fight to free Jake's brother, Tom. He announces that he is quitting in #5, but when he sees his mother is a Controller, he vows to continue on fighting until she is free.
Like Rachel, Marco has a bit of a dark side, which shows up in his (at times) very cold and ruthless schemes. Marco is often focused on the "big picture" (winning the war), sometimes at the cost of the "little" things (his mother, for example). He isn't entirely comfortable with this aspect of himself, but has embraced it as necessary to the war effort. He also struggles between the dream of his mother returning to normalcy and moving on, accepting her for dead. This conflict is revealed in The Proposal. In #10: The Android, he develops a lust for gruesome revenge against the Yeerks, and admits to enjoying being violent (for example, he worries Ax when he tries to kill a beetle in spider morph), even though he constantly derides Rachel's violent habits.
Marco prides himself on an ability to see from A to Z - to chart the most effective plan of action, with morals or values being secondary concerns. This is not to say he is amoral, as he is able to factor in these values and alter the plan accordingly - but he does have the ability to see what needs to be done to achieve goals. In this way, he is extremely valuable strategically.
At the end of the series, Marco has a flourishing post-war life; he has become a celebrity, starring in TV shows, giving interviews, and becoming the unofficial spokesperson for the Animorphs. He deeply enjoys the playboy lifestyle, although he admits to being "bored out of his mind" and does not hesitate to give it all up and join Jake in a possibly suicidal mission to rescue Ax.
Marco is also the only Animorph in the series without a main love interest, though not for lack of trying. It is hinted that he may have a crush on Rachel, and the two do date in an alternate reality in Megamorphs #4: Back to Before.
|Gorilla (Big Jim)||The Invasion|
|Great Horned Owl||presumably The Capture|
|Mouse||The Andalite's Gift|
|Irish Setter||The Android|
|Spider Monkey (unusable: Sario Rip morph)||The Forgotten|
|Jaguar (unusable: Sario Rip morph)|
|Tyrannosaurus rex (unusable: Sario Rip morph)||In the Time of Dinosaurs|
|Cobra (Spawn)||The Discovery|
This is a list of books narrated solely by Marco:
Marco also takes part in the narration of: