Why is this failing to get a playermouse?

for _,v in pairs(game.Players:GetChildren()) do
        thing = script.AnnounceGui:clone()
        thing.Frame.Position = UDim2.new(v:GetMouse().ViewSizeX/200,0,v:GetMouse().ViewSizeY/200,0)
        thing.Parent = v.PlayerGui
    end

It threw an error saying it couldn't index a nil value with v:GetMouse. But I'm definately talking about players with v because I'm iterating through the players. Why is this going wrong?