I thought the same - so looked this up (https://en.wikipedia.org/wiki/Boy_or_Girl_paradox )- there's a section that explains the ambiguity of the question. i.e. did they look for that family with two kids, at least one of which was a boy to ask the question about (in which case pr = 1/3) or or did they choose a random family and then make a statement about the kids in it (in which case pr =1/2).
At least I think that's what it says...
Question says:
"mother has at least 1 boy..."
So GG is not possible, leaving 3 possibilities, BG, GB, BB.
"Out of those possibilities, what's the probability both kids are boys":
Question says:
"mother has at least 1 boy..."
So GG is not possible, leaving 3 possibilities, BG, GB, BB.
"Out of those possibilities, what's the probability both kids are boys":
1/3