Suppose: Xiao Ming is X and his father is X +7n (every 7 days, n = 1, 2, 3, 4).

x+x+7n=38

x= 19-7/2*n

So n can only be an even number,

When n=2, x= 12, x+7*n=26.

When n=4 and x=5, x+7*n=33 (truncation).

A: Xiaoming's birthday is April 12, and his father is April 26th.