Ah, I think I may have gotten the wrong end of the stick.
But, this part still really annnoys me:
"They say the measure would give parents an incentive to discuss the topic before children found out themselves"
I do not think it is the governments place to meddle in when or how parents do or don't choose to reveal this information.
Yes, fair enough, biological information should perhaps be available to people (probably when they are adults, say 18 or so). But, the government has stepped into the world of nanny state if they think it is their role to encourage parents to tell children sooner and not later.