CP,

Get your facts right.

Your coin metaphor is wrong.

Woof clearly stated that both of the 2 children were already begat.

You are wrongly suggesting otherwise when you talk about the 2nd flip of a coin.

The next part of the stated problem, involved X - an information provider (not necessarily a parent KV!) who secretly ascertained the gender of one child. Then if that child was not a girl X then checked the gender of the other to see if that one was a girl.

All that X disclosed was that one of those 2 children was a girl.

You don't know how many childrens' relevant details X examined.

X didn't say that the younger was a girl. Nor that the older was a girl.

KV has wrongly assumed that the parents are informing you that one of the children is a girl.

But you are not making assumptions. Instead you have invented a contradictory scenario.

There is no flipping of a 2nd coin. Both coins have already been flipped.

Enough coins have been examined to truthfully disclose whether a head has occurred.

After I figured the problem through I then googled to see whether this was a classic problem.

Got it in one.

http://mathforum.org/dr.math/faq/faq.boy.girl.html

Meanwhile some of you couldn't even do the right thing and check whether you had read the problem correctly in the first place.

Imagine the response you can expect next time you ask a stats related question.