Their vs There
Quick answer: Their shows possession (their house). There points to a place or starts a sentence (over there; there is). If you can replace it with 'our', use their.
Their
Possessive determiner: belonging to them.
“The students turned in their homework.”
There
Adverb/pronoun: in or at that place; used to introduce a clause.
“Put the box over there.”
How to remember it
tHEIR contains HEIR — someone who possesses. tHERE contains HERE — a place.
Common mistake
'There going to love it' — that's the third one, they're (they are).