Brothers and Sisters Day, also referred to as Siblings Day, is observed on May 31 in some European countries. It was launched by the European Large Families Confederation (ELFAC) to celebrate sibling bonds and relationships. In Europe, Brothers and Sisters Day was launched by ELFAC in 2014 to highlight the importance of sibling relationships in child development. ELFAC was created in 2004 at the 2nd European Large Families Conference in Lisbon. It unites large family's association across Europe, representing over 60 million people from nearly 9 million families. The main objective of ELFAC is to represent the social and economic interests of families with children, with a special emphasis on large families, as the most appropriate environment for raising children and helping them integrate into society as functional members. The Confederation also strives to connect European large families' associations for the exchange of experience and mutual support. ELFAC suggested that Brothers and Sisters Day be celebrated on May 31 because it is the day before the International Day for Protection of Children, commonly referred to as Children’s Day. Besides, some European countries celebrate Mother’s Day in May (usually on the first, second or last Sunday of the month, depending on the country), and May 15 was declared the International Day of Families by the United Nations, so May is truly a “family month”. European Brothers and Sisters Day is celebrated in all countries with ELFAC’s member associations: Andorra, Austria, Cyprus, Croatia, the Czech Republic, Estonia, France, Germany, Greece, Hungary, Italy, Latvia, Lithuania, the Netherlands, Poland, Portugal, Romania, Serbia, Slovakia, Spain, Switzerland, and Ukraine. The holiday is particularly popular in Portugal, where it has been acknowledged publicly by the president. https://en.wikipedia.org/wiki/Siblings_Day