She died without telling him.
There is a specific kind of question that the death of the last firsthand witness closes off. It is the question of why. Why did June and Ethel May make the arrangement they made? What were the exact circumstances of the pregnancy and the decision? What did June feel about it? What did Ethel May feel about it? What conversations happened between them, across the years, about the fact of what they were doing?
These questions did not have an official documentation. There was no letter made public, no diary entry, no deathbed conversation on record in which Ethel May or June explained the reasoning behind the arrangement in their own words. What exists is the arrangement itself, the family structure that Jack experienced, and the general historical context in which that kind of arrangement was made.
Nicholson said later, in an interview, that “only Ethel and June knew, and they never told anybody.” That statement suggests that his own understanding, after the revelation, was that the secret had been held between exactly two people — the grandmother who raised him and the mother who was presented as his sister. Lorraine, the aunt who confirmed the truth when Jack reached out to verify what the Time reporter had told him, apparently knew. Whether John Nicholson, the grandfather who was presented as Jack’s father, knew the full truth or only suspected it or was told some partial version is not clearly established.
The death of June in 1963 and of Ethel May in 1970 created a specific situation in 1974: when the revelation came, there was no one left who had been present at the beginning. The two people who could have confirmed or denied it from firsthand knowledge were both dead. The confirmation that Jack eventually got came from Lorraine — from someone who had known, but who had been inside the arrangement as a family member rather than as one of its primary architects.