I have my cmsms running fine and quite happy with it so far

{news number='5' dateformat="%d %b %Y" category='1_1'}
but what i want is this :
Category parent : 1
Sub category : 1_1
Sub category : 1_2
Page 1 with {news number='5' dateformat="%d %b %Y" category='1_1'}
Page 2 with {news number='5' dateformat="%d %b %Y" category='1_2'}
I want to have only the 1_1 news when the article is written with category 1_1 on the page 1
I want to have only the 1_2 news when the article is written with category 1_2 on the page 2
but i also want to have the news on both page 1 and page 2 when the parent is selected (category 1)
I tried to say something like
{news number='5' dateformat="%d %b %Y" category='1_1' category="1"} but it naturally does not work (naturally because i don't know the syntax, and therefore cannot be successfull at the first try

I fear that inserting {news number='5' dateformat="%d %b %Y" category='1'} under the {news number='5' dateformat="%d %b %Y" category='1_1'} line may split news into 2 different "threads" and i want news to be "altogether"
If my problem is clear enough, is there a way to do what i want ?
Regards