Is it me or is there about 10-12 sans-serif fonts (Lato, Open Sans, Noto Sans, Merriweather Sans, Roboto, Istok Web, Oxygen, PT Sans, Source Sans Pro, Gudea, V

Is it me or is there about 10-12 sans-serif fonts (Lato, Open Sans, Noto Sans, Merriweather Sans, Roboto, Istok Web, Oxygen, PT Sans, Source Sans Pro, Gudea, Varela) -- which are all lovely modern sans-serif fonts -- but are incredibly similar? Are they based on one another, or just similar in modern sensibility?