Good to see them together. And HM is wearing two of the three Indonesian brooches (originally intended to be a tiara, a gift from indonisian sultans to Queen Wilhelmina).
They must know each other quite well as Beatrix was very close to the late king Boudouin (almost 2nd father for Phillipe) and Phillipe also attends the Bilderberg conferences regulary (probably on the invitation/suggestion of HM).