The God of Small Things is probably more than anything else a novel about family. It explores the relationship between brother and sister, mother and child, grandparent and grandchild, aunt and niece/nephew, and cousins. It looks at the ways families are forced to stick together and also how they fall apart. Unconditional family love is a major issue on the table here. Sometimes we feel obligated to love our family members. On the other hand, just because you're related to someone doesn't mean you'll love them or that they'll have your back. Just like in real life, family relationships in the novel can be complicated, confusing, and frustrating.
In The God of Small Things, "family" refers to people obligated to each other because of blood, regardless of whether or not they actually care about one another.
In The God of Small Things, "family" refers to the people one cares about.