Kathy (With or Without You)

Kathy is the sister of Danny.

History
Kathy was raising her younger brother, Danny, after the deaths of their parents.

At some point in his past, Danny received a liver transplant. Later, his body started to reject that liver, so he was in the hospital waiting for another liver to become available for transplant. Alex Karev took the case to Meredith Grey to look for more treatment options. She examined Danny and decided that she wanted to rebuild his biliary tree, which would prevent further infections and give him more time to wait for a transplant and would even allow him to go home while he waited. Danny wanted the surgery, but Kathy was scared of the risks.

When Danny's conditioned worsened, he again insisted that he wanted the surgery. Kathy admitted that he was almost an adult and had very little control over his own life, so she agreed to do what he wanted and Danny had the surgery. In surgery, he had a lot of bleeding, so Meredith put in a shunt, but the anastomosis leaked. They tried to repair the damage, but despite their best efforts, Danny died in the ER. When they told Kathy, she was devastated to hear of his death.

Familial
After the deaths of their parents, Kathy took over raising her younger brother, Danny. She said she'd spent her whole adult life taking care of him and said he was her whole life. When he died, she was devastated.

Notes and Trivia

 * She got a hockey puck signed for her brother, who was a hockey fan.