You can meet the Twin Stars ingame in HKO in Paris - just enter the Pantheon, it's not locked. Both twins will give you some quests. At the Dream Carnival you will find them seperate from each other; Lala seems to be in trouble - help out if you'd like.
You can see the Little Twin Stars once again in New York where they will give you some more quests later on in the game.
The twin stars were devised by Sanrio in 1975.
The Little Twin Stars Lala and Kiki were born on the Star of compassion in the Dream Galaxy on December 24th. With permission from their Mother-Star (a poetess) and Father-Star (an inventor) they are on vacation on Earth. The Twin Stars like to spread happiness to everyone they can meet with their star-powers. They are friends with the sun, the moon, the stars, the clouds, and also with sprites, animals and fairies.
The boy-twin Kiki can fly through the sky using the star on his back, is very curious and a bit boldfaced sometimes. He likes to invent things and liks to fish stars. The girl-twin Lala is shy, loves drawing and writing poems, cries easily, but can cook well; her soups are amazing. Her wand led the Twin Stars the way to earth.