Let me elaborate on swbarnes2’s answer.
The “Possibility of Jane's brother being a carrier” is indeed the trickiest part of the overall question. I have seen that even some teachers of genetics were puzzled when seeing the correct answer (2/3).
It is true that before the brother is born the probability of he being Cc is given by the standard Mendelian rule, ...
And this is the part that I am not getting. For me, Jane's brother
could only have a 1 in 2 chance of being a carrier (Cc or CC).
Wrong, because those are not equally likely.
There are 4 equally likely possibilities for any of Jane's siblings:
inherit good allele from Mom, good from Dad,
inherit bad allele from Mom, good from Dad,
inherit good allele from ...