In a globalised community, don't we have many relatives we do not know and many relatives we have not seen or know of their birth? Do you know your cousin's children (born overseas) faces and names?
Can anyone claim to know all his/her relatives?
What is your point?
So your point is alright for a fellow Singaporean citizen/PR neighbour but not a foreigner to rent out that extra room or are you stating that the government should tax our fellow Singaporean citizen/PR neighbour and foreign owner to make it legal?
What is the foundation of your bias?
Are you envious you do not have spare rooms to offer for rent?