Milia

Milia is Amanda's little sister, who appeared in the second TV special.

Appearance
Milia is a young girl with short orange hair and large brown eyes. She is seen wearing a blue dress with two buttons and a white collar and brown shoes. Her shirt sleeves also have a blue and white striped pattern on them.

Personality
Milia is a fairly calm and collective person. After her father died, she developed a disliking for pirates, but not that to the degree of her sister. She also seems to be very intelligent, since she could find an island with no magnetic field using a log pose.

Family
Milia cares a lot for her older sister, Amanda, and her younger brother, Holy. She and Amanda have taken the role of watching and caring for Holy in the absence of their father. Milia also had a strong bond with her father, but before died, he gave her a log pose, her brother a map reading tool, and painted a map on her sister's back so they could find his treasure.

Maccus and Bonney
Milia began to trust Maccus and Bonney soon after they struck a deal with her sister, Amanda. When they decided to foster the three children, Milia happily accepted them as family.

Straw Hat Pirates
Though Milia had once disliked pirates for killing her father, she developed a liking toward the Straw Hats, saying they were different than other pirates. She has been shown to have a bond with Sanji, looking up to him, and also looks up to Nami.

Abilities and Powers
Milia has been shown with fairly basic navigation skills and seen using a log post.

Past
During her early childhood, Milia's father went on many great adventure to find treasure for his children to make them happy. When her father returned from one adventure, he had a fatal would given to him by Bayan. Milia's father gave her a log pose, her brother a map reading tool, and drew a map on her sister, Amanda's, back before he died.

About a month before meeting the Straw Hat Pirates, Milia and her siblings here captured by Zap. When Maccus and Bonney were moving cargo, they came across the children, and Amanda struck a deal with the two to go to and island where her father's treasure was. The five of them escaped Zap on a small life boat and traveled to the island to find the treasure.

Open Upon the Great Sea! A Father's Huge, HUGE Dream!
When the Straw Hat Pirates arrive at the island and Maccus, Bonney, and the children are hiding, Holy runs out of the clearing to chase something, and Milia catches him and stops him from getting too far away. The Straw Hats see them and Maccus, Bonney, and Amanda make up a story about them being a family of campers. They all have a conversation about the "camping trip" and Milia comments that the Straw Hats don't act like normal pirates. The story is broken when Amanda runs off after Usopp talks about their great adventures, filling her with sadness and anger over her father's recent death. Maccus and Bonney take the crew to their temporary cave home, talk about the children's father's treasure, and Milia tells them about the island's magnetic field and her log pose. Afterwards, they all go onto the Straw Hats' ship and have a feast.

The Bayan Pirates then arrive on the island and capture Luffy and Amanda, causing the Straw Hats and Maccus, Bonney, Milia, and Holy to follow Zap's ship. They arrive at Bayan's ship, where a battle between the Straw Hat Pirates, Maccus, and Bonney against Bayan, Zap, and the pirate choir ensues. The Straw Hats win the battle and Amanda is freed.

The Straw Hat Pirates, Maccus, Bonney, Milia, and her siblings go back to the island, and with the help of Luffy, Zoro, and Sanji, reveal the island is inhabiting a giant clam and that their father's treasure was a giant pearl. Maccus and Bonney then take Amanda, Milia, and Holy in as adoptive parents and they form a family.

Trivia

 * Besides looking very similar to Nami, both Milia and her have interests in navigation.