7.
The prime factorization of 567 is 3.
Since there are four factors of three, there are three ways mathematically to multiply three numbers, with two equal, to get 567:
167 = 567
33 = 567
9 = 567
Of these, the first is impossible, the second is maybe possible, but the third is the only really plausible answer, and that is what we are looking for.
The twins are 9, and the other brother is 7. |