How do relationships create community?
Relationships create community by connecting people and having more people meet other people. By doing so, in a certain community other people will move in to the community and join the people they love or join their friends. By having family and having another kid you may have to move to a bigger house and the relationship makes the community bigger. If you move from another state and you hear good things from a friend that lives in a certain place. You then might want to move there because of your good relationship with your friend. Just like xavier says friendship builds community.
Another example is maybe you have a good relationship with your community. Always giveing a good word about the community makes other people move in. You might get a new job and need to move. When you move you might move into the community where the job is located. The job relationship also brings more to the community. Whether it is bad or good, many relationships bring more to the community. These are types of relationships that bring more family and love to the community, but I think there are many many more types of relationships that also bring love and family. For more examples read what Darvin has to say.