In terms of pronouns acting as attributives indicating possession, we usually add 的, e.g. 你的书 (your book)、我的杯子 (my cup). If the noun to be modified is a country, organization, or relative, sometimes we do not need to use 的，e.g. 他们国家（their country）、我妈妈 (my mother)、我们公司 (our company).

In this case, 家 is related to one's family members, relatives and it is also like an organization in a sense, so we don't need to use 的 - instead we just say 你家. Hope this is helpful!