This is really headache sia...
I have to look at the whole family: You get along with your
Grandfather? If so it should be easier: just kindly advise him,
tell him consequences, not to ruin his life etc... something like
asking him to quit smoking... Grandparents on the whole dotes on
grandchildren, so it might be possible to strike gold if this is
the situation.
If possible, ask him to join the "le lin" club. That should keep
him busy enough to keep dirty thoughts off the maid.
Er.... if both of you all are on rocky terms, theres no harm in
advising also... but your family will have a "conscience heart" to
report to the proper authorities if anything nasty happens...
Seriously, I also very struck... If my advice can help you, then
great. Else.... I also don't know... sorry.