Questions & Answers about Ist deine Familie groß?
Why is it deine instead of just dein?
In German, possessive words like "your" have to match the gender of the noun they describe. Because Familie is a feminine noun, we add an -e to the end of dein, making it deine.
What if I wanted to ask this question formally to a stranger?
If you were speaking formally, you would use the formal word for "your", which is Ihr. Because Familie is feminine, you still need to add the -e ending, making the question Ist Ihre Familie groß?.
Since Familie is feminine, shouldn't groß have an -e at the end too?
No, because groß comes after the verb ist (is) to describe the family, rather than sitting directly in front of the noun (like in "a big family"). When adjectives are used this way at the end of a sentence, they never get gender endings.
Why does the sentence start with the verb Ist?
Just like in English, you form a simple yes/no question in German by moving the verb to the very beginning of the sentence. A regular statement would be Deine Familie ist groß (Your family is big), so swapping the verb and the subject creates the question.