She is believed to be the daughter of Queen Jaydes and King Grambi, and she runs away a lot to escape her overprotective parents. She does not know why her parents are so protective, but it is later revealed that she is really a Pure Heart; Jaydes and Grambi transformed her from the Pure Heart into a living form to protect it, as "no one would suspect" a Nimbi to be a Pure Heart (though Bonechill did somehow find out about Luvbi's actual form). They admit that, over time, they grew to love Luvbi and felt as if she was their real daughter. Luvbi speaks in Early Modern English (as do all Nimbis), and is constantly putting others down, namely Mario, Princess Peach, Luigi, and Tippi.
Even though she changes into the Pure Heart at the end of Chapter 7, Luvbi can be seen standing next to her parents in Grambi's shrine if the player chooses to return to The Overthere after completion of Super Paper Mario. When spoken to her, she states that even she does not know how she exists as a Nimbi again; it is even stranger to note that the Pure Heart version of Luvbi can still be seen in its Heart Pillar even after Super Paper Mario is beaten, making it possible (though very unlikely) that one of the Luvbis is an impostor, or that the Pure Heart may have granted the wish of Luvbi's previous form to become a real Nimbi.