Family Systems Therapy (FST) and its sub-branch Structural Family Therapy (SFT) are both psychological approaches that focus on the family as the most important unit of social organization; both analyze the relationships between family members as the key information in the process of creating healthy and stable individuals. FST treats a family as a singular emotional entity, with the same approach that traditional therapy might use to treat a single individual. In SFT, the psychologist "joins" the family and seeks to identify dysfunctional patterns within its power structures and then reorganize them along healthier lines. 

Since The Blind Side is about the welcoming of Michael Oher (young, black, and homeless) into the Tuohy family (white and affluent), we begin the movie viewing two dysfunctional family units—Michael's and the Tuohys. We are led to believe that, through the movie, harmony is achieved by the two merging together and offering the other something that was not available before. 

Michael Oher's is the simpler "problem"; he has no traditional family. And because of this, he does not have access to the great deal of support that healthy families are able to offer each other: emotional support, access to education, access to love, food, shelter (he has never slept in a bed), etc. 

Leigh-Anne Tuohy has a more nuanced "problem." Her family unit is comfortable but closed. Michael opens her up to a world she has not known before and changes her views on class, race, and more. 

Beth: You're changin' that boy's life.
Leigh Anne Tuohy: No. He's changin' mine.