The words "their," "there," and "they're" are homophones: they sound alike, but they have different meanings. Keep the different definitions in mind when you spell these words.

"Their" is a personal possessive adjective that means "belonging to them."

My friends brought their dog with them. [The dog belongs to them.]

"There" is a word that takes several parts of speech. It is most commonly used as an adverb meaning "in that place."

I put your book there. [I put your book in that place. The adverb "there" modifies the verb "put" and answers the question "Where?"]

As a noun, "there" means "that place; that point."

If you drive halfway, I will take it from there. [I will take it from that point.]

As an adjective, "there" means "able to be relied upon; fully conscious or aware." These meanings are usually part of the idioms "there for (someone)" and "all there."

My sister is dependable and she is always there for me. My brother is a flake; he's not all there. [My sister is able to be relied upon and my brother is not fully aware of things.]

"They're" is a contraction of "they are."

They're my siblings and I love them both. [They are my siblings.]