Later on, we find out that Zhang Ziyi’s Ilene Chen comes from a family of female Monarch employees who all bear a striking resemblance to one another and either worked, lived or were born on a place called Infant Island.
Giving Ilene Chen a twin that she never interacts with might seem like an odd choice, but it is actually a deep Easter Egg into Toho History.
Dr. Ling Chen is Ilene Chen’s twin sister. This isn’t really acknowledged at all in the film and audiences aren’t given much of an explanation.