Did you read the link ?? 
.... the only instance when single PRs can
apply for an HDB flat, is when they are latched onto the
application of a Single Singapore Citizen applying under the
orphans scheme. Under the orphans scheme, single singapore citizen
siblings over the age of 21 can (infact, it's designed for ) own an
HDB flat too.
And, we are all talking about resale flats here, since new HDB
flats, are reserved for Singapore Citizens and their family units
only.
Two siblings are not eligible under the public scheme, as, I've
pointed out, they don't constitute a family unit according to the
rules. whether citizens or otherwise.
PRs definitely didn't get preferential treatment over citizens.
Infact, if anyone actually bothers to scroll through the HDB
eligibility documents, he'll notice that almost all of these
schemes, and ALL of the subsidies, are reserved for Singapore
Citizens only.
Fatum, I suggest you do a simple google search with key words
like "PR siblings scheme resale flats" and have a look at the
online chatter for the past few months regarding this issue.
There are just too many to link and direct you to. 
