Seems to have been a bit of confusion in several directions here, but just to clarify: in modern usage 金子 is read only as Kaneko, and is a very common surname.

Seems to have been a bit of confusion in several directions here, but just to clarify: in modern usage 金子 is read only as Kaneko, and is a very common surname. The "kinsu" reading is archaic; a typical native speaker may never have heard of it.