In terms of politeness, manners, and etiquette, I don’t think there is a “right answer” to your question. At best, it’s a bad pickup line. At worst, it’s downright creepy.
In terms of English and grammar, though, I think this question is often asked beginning with a Where, rather than a Who:
Where did you get your good looks [from]?
For example, in one blog post, the writer asks:
One of the most common questions I get asked, other than "Where did you get your good looks from?" is "Have you always wanted to be a jeweller?"
(Note: I don’t think the author really gets asked that first question; I think it’s just an attempt at clever humor. However, it does provide a fitting example of how the question is sometimes phrased.)