Make use of relationships on recommendation systems I have a data set of user rating for movie as

user_name, product_name, user_rating


and I am using this data to recommend new movie to user (collaborative filtering). 

I also have another data set which show relationships between user like

user_1, CO_WORKER, user_2
user_1, FATHER_OF, user_3
user_3, FRIEND_OF, user_4 etc


Now what are the ways to include 'relationship data' along with 'ratings data' to produce better recommendations ?

example : user_1 might like the movies which user_2 likes since they are co_workers
There are a number of ways to make use of this information, including various graph-based methods of recommendation.
Collaborative Filtering using Weighted BiPartite Graph
Projection
A Recommendation System for Yelp
It's also common to use multiple approaches to build a hybrid recommendation system.