iOS is OSX under the hood, it's the same core OS kernel, just the userland is different with a different API. The same goes for WatchOS. The same can be said f

iOS is OSX under the hood, it's the same core OS kernel, just the userland is different with a different API. The same goes for WatchOS. The same can be said for Windows (7/8/10) and WinPhone8+ and XBox, all run a Windows NT kernel with different userland and APIs. And Android and ChromeOS have the same OS under the hood too, modified Linux kernel with different userland.