Assuming Mrs. Wenzl is the grandmother, let the digits in her age be m and n
m is odd, because the sum is odd, so m=1,3,5,7
Now, m=1,3 are not likely, since that would make for a very young grandmother.
So, if m=5, then 55+2n=83, and n=14, but that can't be, since n<10
That means m=7, and 77+2n=83, so n=3
So, the siblings are 7 and 3, and the grandmother is 73