There are three possibilities here:
1 This is a child whose DNA has mutated in more than one gene to produce a child who is Caucasian, blonde, and blue eyed , but has no other signs of mutation or birth defect.There is not one single way that I can think of that would make this possible.
2 The wife has found another sperm donor, and the husband is gullible.
3 This story is a hoax.
Occum’s razor tells me which of these is the least likely.