Seven-year-old Aiden McCullough and his 20-year-old sister, Morgan Smith, are very close.
"I love my sister a lot," McCullough told WAWS-TV.
Now, their bond is unbreakable.
"That's my hero. My angel. My brother," Smith said.
The siblings were swimming in the pool at their home in Brantley County, Georgia last week when Smith suddenly had a seizure.
"I was thinking like, 'oh my God, oh my God, she's going to die,'" McCullough said.
The 7-year-old says his instincts kicked in. He grabbed his sister's hair and held her head above the water.
"I would've drowned," Smith said.
Smith says her brother is brave.
"I know that there are real life angels because I'm lucky enough to call him mine. I have an every day superhero in my life," Smith said.
Smith says she's thankful McCullough was in the right place at the right time, and ready to step in to help when she needed her little brother the most.
"I love you and you are forever my hero and every day I'm only more thankful that I get to call you my little brother," Smith told her brother.
"I love you always, too," McCullough said.
'My angel, my brother:' 7-year-old Georgia boy saves sister after having seizure in pool