JohnF. Can you give your source for this reading, please? Hayashi Yutaka gives Kouhara Masahiro in his Go Encyclopaedia. Given his job as Kido editor, I think we can be fairly certain he knew the son personally. Admittedly, Hayashi also gives the death date as Taisho 11 (1923)-11-1, so we can't assume he's always right.
hnishy: My pleasure. First for the father:
1) https://kotobank.jp/word/%E9%B4%BB%E5%8E%9F%E7%BE%A9%E5%A4%AA%E9%83%8E-1074235 This site shows the pro as Konohara, based on 日本人名大事典 by 講談社. It has no readings for his later personal name 正広.
2) https://dl.ndl.go.jp/pid/1879491 大日本人名辞書 上卷 新版 (1926) shows his name as コウノハラセイクワウ Konohara Seiko. These contradict with Hayashi. Hayashi started his journalist career only after the war. And for the journalist:
3) https://dl.ndl.go.jp/pid/2517088 囲碁風雲録 : 昭和の大勝負 Hayashi himself writes 囲碁ライター鴻原は木谷の旧師の子であった in a paragraph about the Shin-fuseki. This 旧師 (previous teacher) is the pro. So the journalist was a son of the pro.
Some mysteries remain. We may need to add some notes on this matter. Konohara is a rare reading of the name, prone to misreadings. Maybe the son changed it to Kohara and Hayashi naturally believed the father was also Kohara.