Almost every single men and women in the late of twenties heard this sentence. It's a question asked by relative and closed friends as they wants you to be happy. However, hearing it over and over may make you any thing but happy.
what is the proper answer
If you are still single, tell that person that you haven't found the one who you want to spend your life with.
But, if you see that the question is nosy , for my self i would change the subject.
tell me what will you say if you asked this nosy question?