Yes, if they are internally connected like that and you feed one multi-cap into the other (with the balancing resistor connection in the middle), then that's fine.
I was looking at a circuit digram and seeing one capacitor above another, had the mental picture of that's how the two capacitors were arranged in the common can. But its the side by side caps that are the common can, with one can connected to another/feeding into the other.
Yes, you then get about 250v across each capacitor, so a 500v rating is perfectly safe (providing the resistors don't loose their ground connection or a cap doesn't go short circuit - but you can't allow for every possible failure scenario).
With the way you've drawn it, it makes much more sense to me.