Question: From death to brittleness?

Two bodies, on a bed, in an embrace. Windows and doors closed, so little to no air and light, but not completely air/light tight.
No scavenger animals/rodents, but bugs would obviously be present.
Humid (tropical rain-forest) environment.

The aim is to have my characters stumble across this old castle, and find the bones of two people on the bed. I don't care if the bones are touched they would fall to dust, or if they are moved slightly/disturbed by bugs, or even if some of the bones are dust already, as long as it can be made out that its two skeletons embraced together. (and if not clearly embraced, its at least clear that its two skeletons)

(i know "dust" isn't the appropriate term here, but you get what I mean?)

How many years could this take?
Thankyou

EDIT: Just wanted to re-iterate, I don't so much care about the decomposing bodily fluids and flesh. I know that will decompose and be eaten by bugs and will stain the sheets upon decomposition.

I know that mummification is out, as of the humidity.

I'm wanting to know what happens to the BONES well after the process of rotting flesh is done. I know the joints wont stay together, and I know that the bugs will move the bones around a bit if they are eating the flesh. But say that, after a month or so of the people being dead, their bones would still be on the bed, and it would be obvious that two people were on the bed together, even if not embracing?
how long would it take before their bones became so fragile and brittle that they would turn to "dust." or upon discovery of the bones, and disturbing the bones, would they disintegrate to dust upon a rush or air or a touch of hand?

Answer: 
They discovered [Richard III's](https://en.wikipedia.org/wiki/Richard_III_of_England#Discovery_of_remains) bones a few years ago. Given that he died in 1485, bones do survive for around 5 centuries in soil. 

Flesh rots in air, bones desiccate. From what a quick Google search indicates, bones become powdery in air in around 50 years. That said, I would guess, given a lack of air movement, and no animals crushing them with their weight/gnawing on them, the bones should retain their shape indefinitely.
The rule of thumb is “100 degree-days to get bones”. I don't know what *degree* is measured from, but that should be a start for Google…

And that turns up [this link](https://weather.com/science/news/flesh-bone-what-role-weather-plays-body-decomposition-20131031) which is a start. [This one, *The Rate of Decay in a Corpse*](http://www.exploreforensics.co.uk/the-rate-of-decay-in-a-corpse.html) is more informative and provides the vocabulary you will need for further searching.

Just skimming, the lack of rain or direct exposure and not being directly connected to the soil will reduce the decay rate. Depending on conditions you may bet a mummy and not a skelleton.

So allow for **rats** or other wildlife to get in from a wooded area, as well as flys and beetles. That's the opposite of what you specified, so you can expect dessicated remains with nothing happening after flys. You might postulate specific carnivorous beetles, but really you wrote yourself into a corner. Where would the flesh hqve gone off to?