wrote:

The probability that a hypothetical couple (HC) who will have 2 kids
will have one of each is one in two.
The HC's children will either come out as: BB, BG, GB, GG. 4
possibilities, each equally likely, 2 of the 4 possibilities give you
one of each, 2/4 = 50% = 1/2.

Spoilsport :-)

--Helen