This would be unlikely since the Togakure school is probably a reconstruction/invention derived from Kukishin and a great deal of original research from Toshitsugu Takamatsu.
There are many instances of people discovering ninjutsu related documents in their family, but ninjutsu is fundamentally a set of Sengoku-period strategic techniques and not so much hand to hand fighting.
You might have informal training passed on within families, but a Ryuha is fundamentally a social institution that, while passed from one family member to another, are really only family managed and not "exclusive" -- if it's just in the family, the whole Ryuha system is unnecessary.
I mean, if your Dad teaches you a few tricks it's not really a "secret family martial art."
I was wondering if you were aware of any "family only" ninjutsu teachings. Teachings passed down from father to son or uncle to nephew etc with the teaching of outsiders (non-family members) a strict no-no ??
I have an older japanese friend who claims he has been trained in ninpo taijutsu by his father and it is an off-branch to the togakure from about 300yrs ago.
I do bujinkan and he should me some 1stdan techniques similar to bujinkan but his techniques with faster variations that involved more punching strikes and more circular motions.
In your research have you ever come across this? Is father recently passed away so he has now moved back to japan to work on the family farm so i can't quiz him anymore.
Any information you have regarding "family -only" ninjutsu splintering from the togakure about 200-300years ago would be helpful. Or can you point me in the right direction.