The male protagonist of 'My In-Laws are Obsessed with Me.' A handsome man with black hair, red eyes, and a slicked-back pompadour style. He is the youngest of three siblings and inherited the title of Grand Duke after his older brother's death. Hair Color: Black The current head of the Grand Duchy of Lapileon. He is at the forefront of suppressing wars and rebellions. The Lapileon family carries an ancient curse where their blood is poison. Therdeo also has toxic blood and accidentally feeds it to Pereshati when she comes to propose a contract marriage. When Pereshati collapses, he assumes she is dead and intends to bury her, but upon seeing her wake up unharmed, he feeds her his blood again as a test. After realizing that Pereshati is immune to the Lapileon curse, he enters into a contract marriage with her. Over time, he falls deeply in love with Pereshati.

The adopted son of the two protagonists and the heir to the Grand Duchy. Hair Color: Black Therdeo adopted Celphius to ensure the succession of the Lapileon family. Therdeo sent Celphius to a separate villa out of a desire for the child to grow up freely in a good environment without pain. However, because Therdeo rarely visited or spoke to him even at the villa, the servants there often gossiped about Celphius. Consequently, Celphius developed a habit of enduring everything to be recognized, believing the Grand Duke only adopted him because he needed an heir. He gradually comes to follow Pereshati sincerely, viewing her as a mother. Later, Pereshati gives him permission to call her 'Mom.' He also takes good care of Islet, who is around his age and was rescued from abuse, treating her like a real sister. He was the first member of the Lapileon family to open his heart to Pereshati.

The Grand Prince of the Lapileon family, the family physician, and the uncle of Sersia and Therdeo. Hair Color: Black A talented individual who researches the Lapileon curse and prescribes medicine. Several members of the Lapileon branch families work under him. In his youth, he ran away from home to avoid marriage under the pretext of researching the curse. When he returned and found his eldest nephew had passed away, he intended to leave again, but stayed because he couldn't bear to leave Therdeo alone. He has effectively served as a father figure to Therdeo. However, regardless of his decision to stay, his feelings toward his mother seem poor. When he suggested that Therdeo let Pereshati go, Therdeo addressed him coldly as 'You,' stating that someone who once left the family has no right to say such things, suggesting unresolved tension between them.

The first Grand Duchess and the grandmother of the current Grand Duke, Therdeo. Hair Color: Silver She is well-known throughout the empire; first, because she married a man from the same family (though distantly related), and second, because she was the only one to engage in social activities from the reclusive Lapileon family. She currently resides in the Grand Duchy after passing the title to Therdeo. It seems she did not have a good relationship with her husband. Phineas recalls her arguing with him when he spoke of duties to his second son in preparation for his and the eldest son's deaths, and she once ordered her husband's portrait to be turned face-down. She feels pity for and tries to be as considerate as possible toward the branch family members like herself, but she is said to be equally strict.

The former heir of Lapileon and Therdeo's older sister. Hair Color: Red After her brother died and a new head had to be appointed, she wished to start a family line free of the curse, beginning with her own child. Just as she felt this wish might come true with her husband's support, tragedy struck. Her son, thinking it looked uncomfortable for her to wear gloves every day, pulled them off. While she was cooking for her husband and son in that state, a tiny wound on her hand caused both of them to die. Due to this, she gave up the succession and fell into a state of madness. Since then, she has been gradually recovering while managing the Lapileon family's businesses. She was the second member of the Lapileon family to open her heart to Pereshati.

A tragic princess who was born weak and was slowly dying, unable to leave her sickbed. It is said she recently recovered and rose from her bed. Because the Emperor pushed for a marriage between Dodorea and Therdeo, Therdeo hurriedly held a wedding with Pereshati. She shows an unusual obsession with the Grand Duke, whom she barely knows, and displays hostility toward Pereshati. She often appears to have no moral compass, making delusional claims such as saying countless people, including herself, suffered because of Pereshati's intervention. Dodorea's true identity is the witch who cursed the Lapileon family. The real Dodorea died after her body was taken by the witch, but she watched the Lapileon family—who were essentially headed for ruin due to the curse—even in death. To save them, she caused Pereshati to regress and appeared in Pereshati's dreams to reveal the whole truth.