Yes, hereditary occupations eventually makes for a caste (varṇa) within 7th generation if followed successively generation after generation.

Yājñavalkya (1.96).—‘Caste becomes elevated during the fifth or the seventh generation; similarly after five or seven generations one acquires that caste of which he has followed the occupations.’

And this makes a complete sense, for it's obviously improbable that all of my forefather since creation were Kṣatriya-s. Of course, I have a record of all my paternal ancestors back to the mighty Jayachandra but I don't have any proof that they all married within the same varṇa? Moreover, what about ancestors prior to Jayachandra?

Yes, hereditary occupations eventually makes for a caste (varṇa) within 7th generation if followed successively generation after generation.

Yājñavalkya (1.96).—‘Caste becomes elevated during the fifth or the seventh generation; similarly after five or seven generations one acquires that caste of which he has followed the occupations.’

And this makes complete sense, for example (might not take literally), it's obviously impossible that all of my forefather since creation or even current manvantra have been Kṣatriya-s. Of course, I have a record of all my paternal ancestors back to the mighty Jayachandra but I don't have any proof that they all married within the same varṇa? Moreover, what about ancestors prior to the Jayachandra?