"Sometimes foreshadowing is obvious"
I'm willing to bet the other three have pink, red and purple versions of the heart-shaped pendant and they do something when put together in a four-leaf clover shape like the company logo.
Their parent is definitely the president of the company. Probably this meeting was also orchestrated by them.
Theory:
When their parents had them they thought they couldn't maintain a life with four babies while being a president of a large company, so they left them in facilities, but they didn't want a risk of them being ripped apart in the system, so they made it so they were never together. Then they supported them by raising their living conditions.