Joseph E. Robinson preserves mention of Olive Frost having a child by Joseph Smith.
Joseph E. Robinson, Journal, October 26, 1902, 25–26, MS 7686, Church History Library
During the afternoon I called on Aunt Lizzie [Mary Elizabeth Green Harris]–finding her not quite so well but cheerful etc. She told me again of the attempts made by the Josephites to get her to deny the fact that she knew Joseph Smith had more than two wives. Said he married a Pratt girl <and> that Olive Frost had a child by him <and> that both died.