Find followers and people user follows who use my app (twitter ios api)

I'm building an app that uses Twitter as a sign in options. I want to be able to find user's followers and people whom user follows who also use my app.

I only need the id so I can look up in my database. This is doable with facebook graph api, but I'm stuck with Twitter. One way to do this is to get the entire list of followers and followings and search in my database, but this is not efficient.

I also use Google Sign In. if anyone knows how to get user's contacts in the same manner, that'll be awesome.

Thanks