The WA Twin Register was established in 1997 and comprises all volunteering multiples - that is, twins, triplets, quadruplets and quintuplets - born in WA from 1980 onwards. Multiples who have already joined the Register have taken part in a number of research projects looking at asthma and allergies, behavioural problems, early language development and the impact of loss and grief on multiple birth families.

The WA Twin Register is the only population-based register of twins and other multiples in Australia, and one of a few twin-family registers anywhere in the world.