There is
two thing you both can do - one is resigning to fate, the other is
fight for your own happiness.
Resigning to fate and he marrying to another girl and all that crap
- I think its totally lame. Marriage is sacred - its neither a game
n or a deal (humans are the one who made it seemed like that -
which totally degrade and desecrate its highest meaning). He will
probably divorce his chinese wife - or continue to date and have
affair with you secretly. This will NOT only hurt his poor wife,
but rather how long does he wants to keep it going? What if there a
child already? & there are many implication of divorcing, what
if the parents flared up and stop him not divorcing her because of
you? Isn't it walking back to the same problem? 
My take is take on this, but fight rationally. Solve problem from
its roots and not its surface. There are WAYS - give it up and
follow blindly will only cause resentment, regrets and intense
relationship with the three of you. Both of you probably have
karmic relationship with one another - cause such a major rift and
issue in your relationship after so long. No relationship is smooth
going without its cosmic lesson and true love is often the ones
that hits the strongest.
What to do? 
I advice you to tell him to stationed into passive mode. There is
absolutely no hurry for him to get married - delay that. His mum
wants him to get married to those chinese girls - tell him that he
has no chemistry. Your parents will still be parents - they will
disprove someone they don't fancy to be good, but they wouldn't
force you into a hell pit if you really don't. Keep delay time -
reduce her parents resistance against him marrying/dating/etc you.

His parents will give up one day.
I know the issue here is about his parents being gald or not - try
throwing in communication first - if all fails, employ strategy and
schemes. NEVER ATTEMPT MARRY SOMEONE YOU DON'T LOVE and create
another karmic relationship with another person. 
Case
study:
I had this uncle who fell deeply in love with my aunt, who is a
Malay. Female side parents totally forbid her to date him, in the
end also cannot stop her. Then when it comes to marriage - he has
to change his religion, which my uncle doesn't wished to. (He feels
marrying her and changing religion is separate issues
altogether.)
Guess what? He took my aunt to ROM and register themselves. The
parents was furious and totally raging. They leave them as it is
first, and try communicating.
Now? They already had two kids; My older cousin already finished
Army and working - 20++ years old. Of course now already calm and
peaceful already. (Please lor, kids already so big - parents
themselves resign to fate.. LOL) 
When there is a will, there is a way - nobody can
stop a couple truely in love away. *Snarling*
Cheers