Family-Package names are private and aren't accessible to everyone.
All you can do is Launch uri specific to some content or a file format :
In this How to launch my app via NFC tag? i've discussed a way to reegister ur own uri .. so if any app on the platform registers itself with the format .. u can launch them ..
This post shows how to open up an fb app :
How can I open the Facebook App for sharing a link on WP8?
It works if you try and match .. i had an app that opened whatsapp in wp8.1
I used await Windows.System.Launcher.LaunchUriAsync(new Uri("whatsapp:"));
well if you are trying to open apps of a specific file format like PDF then there is seperate uri scheme to it .. MSDN has great documentation on it ..
https://msdn.microsoft.com/en-us/library/windows/apps/mt228340.aspx