Two people asking this question now! I once had a blade by this smith and probably did my search among Japanese sources, mainly on the internet. I found contradictory material and ended up somewhat confused, tracking across the changing names. For this reason I wrote, this will be a 'fun' search! I probably searched through various Meikan too.
This Aoi Art auction page (for example) shows a '3rd Generation' wakizashi, from around Kanbun, and they say there were 13 generations of them from the start of Edo, but the NBTHK paper shown below that says, for the same blade, like yours, 後代 'Later Generation' Harima no Kami Fujiwara Teruhiro.
輝広の初代は慶長頃で作品は極めて少ないが、
本作は3代目が作ったものである。
その後も13代までの間一門を継続する。
AS21594-脇差:播磨守藤原輝広作(3代) – 日本刀販売の葵美術 (sword-auction.com)
Perhaps Aoi makes this assumption from the overall shape of the blade, i.e simply 'Kanbun Shinto'.