Terry Nowell.

[Terry never told him not to tell anyone about this, but he leaves out the part that isn't relevant, the demigod part.]

He told me he was a clone of someone very powerful, and he seemed pretty serious about it.

So, if your person is also named Terrence and sounds like him, but it had to be someone Minato met... then the person who was cloned to become Terry is probably somewhere in your Hirajiro.