Learning if you hold dual citizenship in multiple countries typically requires research into your lineage.
Dual citizenship holds a variety of benefits. You are able to travel on more than one passport enabling you to cross more borders visa-free. You can live and work as a citizen in more than one country and intentionally enjoy the benefits of both nationalities: health care, working holiday visa schemes, education. Citizenship law varies greatly from country to country and does not always overlap – or agree. Learning if you hold dual citizenship typically requires research into your lineage.
Research your lineage. The only way you would discover that you are a dual citizen is if you hold another nationality by descent. Gather a list of countries that you, your parents and grandparents were born in.
Use the internet to research the citizenship laws of the countries listed. Visit the government websites of the countries listed and visit website of the agency that controls immigration.
Understand the complex citizenship laws. Many countries have laws that pass citizenship through generations even if you were born outside of that country. Most countries grant automatic citizenship to anyone born on that country's soil.
Apply for proof of citizenship with any countries for which you have a connection. Some countries will only allow you to gain your citizenship if you apply by a certain age, prove a connection to the country or take up a physical residence inside the country. You will be required to gather original documents proving your citizenship, including birth certificates of relatives, marriage certificates and proof of physical presence inside a country.
Some countries, including Singapore, require compulsory military service and the renunciation of all other citizenships in order to obtain Singapore citizenship.