They won't have to be, but you can be sure there will not get residency visas of any sort if the children were born to Singaporean parents (whether by birth or otherwise) if said birth were after the parents gained Citizenship in Singapore (This especially so in the case of a male child due to to obvious circumventing of National Service (appearance is everything even if it were not the purpose). Additionally, the only way the children would be able to gain foreign citizenship is if the country of birth allow citizenship by birth (jus soli) (Singapore, for instance, does NOT unless one parent is a Citizen of Singapore at the time of birth of the child. If neither are citizens of Singapore but are here working, etc., the child will not gain Citizenship here without jumping through all the hoops. Lots of countries do not give foreigners born in their country automatic citizenship by birth (jus soli I believe). Even the US has tightened up to some degree now.
Is Singapore a jus sanguinis or ius soli?
To acquire citizenship by birth (jus soli), the person must be born in Singapore and either parent must be a Singapore citizen. For citizenship by descent (jus sanguinis), the transmission of citizenship from generation to generation was not always automatic but only available in specific instances.
