Complex sentence: Stoneheart and the Brotherhood come across a small party led by Brienne, who informs Stoneheart that she is searching for Sansa at Jaime Lannister's request.
Split into simpler sentences: Stoneheart and the Brotherhood come across a small party led by Brienne. Brienne informs Stoneheart that she is searching for Sansa at Jaime Lannister's request.