Google has started to display social media accounts other than G+ for the businesses and brands in the knowledge graph box, as reported by Search Engine Land.
Right now, Google is pulling profiles from Google+, Instagram, Facebook, Twitter, YouTube, LinkedIn, and MySpace & displaying only the most relevant ones while responding to the user's search query.
Google enabled an expansion of the feature for pop brands, artists, and certain public figures in November.
If your business is missing a profile or the search is pointing to a result that isn't your preference, you can add structured data markup to your site by using schema.org vocabulary and JSON-LD markup formate. Google has also given a help document t sharing instructions on how to do that. Some of the basic requirements are:Brands & Businesses: Use Structured Data Markup to Add or Modify Social Accounts in Knowledge Graph,