Wollongong twins Lillian and Charlotte Harding had a thrilling royal encounter on Saturday.
Denmark's Crown Prince Frederik and Princess Mary were at the Sydney Children's Hospital in Randwick to hear Dr David Champion talk about new research affecting twins, including restless legs and an important organic chemical in the brain called dopamine.
Vitally interesting stuff to Princess Mary, who was making her first visit as international patron of the Australian Twin Registry and is the mother of twins left back home.
As the lecture was about to adjourn to the playground to meet some Australian twins, the princess said: ''Can I just ask a quick question?''
''If you increase the dopamine levels ... can you do that? Will that therefore reduce pain?''
The answer was, it could.
Outside everyone was seeing double, with identical twins dressed, well, identically.
Lillian and Charlotte, aged eight, were one of several asked by the prince if they would like to see his latest pictures of his twins Josephine and Vincent, almost three, on his phone.
''I said they are so cute,'' said Lillian.
''I said they are so adorable,'' said Charlotte.
Children remained the focus at the next stop at Randwick library for the launch of an anti-cyber bullying program by the Alannah and Madeline Foundation.
Addressing the group, Princess Mary said: ''Home is no longer a sanctuary. Bullying has moved from an issue confined to school hours, to an issue that can impact children every minute of every day," she said.
"Children, in particular, face significant risks in the online world, including cyberbullying, identity theft and the threat of exposure to sexual predators.''
Communications Minister Malcolm Turnbull said the government was establishing a children's e-safety commissioner to be a single point of contact for those concerned about dangerous material online.
Prime minister Tony Abbott, who met Prince Harry earlier this month, said he was ''thrilled'' to be in the presence of royalty and that Sydneysiders were ''born again monarchists'' in light of the royal visit.
''I'm particularly thrilled to be in the presence of your royal highnesses,'' he said in front of the assembled crowd.
Prince Frederik, asked earlier as he left the hospital how his own twins were, told Fairfax: ''They're good. We miss them.''