Very interesting letter. Funny reading the old-time Watchtower belligerent style. It has a certain nostalgic charm.
Plus, as often with Watchtower, it's more interesting what they don't say than what they do say. They say congregations reported back that no member of the family is a baptised JW. Which is clearly not the same as saying they have no JW connection whatever. They say he was unknown to the Watchtower Society. They don't say he was unknown to the congregations they consulted. I don't think the ambiguity is unintentional. I assume this means his family had some JW connection, possibly as long-time Bible studies and KH attenders. But they don't spell that out.