Marty

Marty is a friend of Keith Kalber who donated a kidney to him, the first HIV+ to HIV+ kidney transplant since the law changed.

HIV
Marty was diagnosed with HIV and spent years fighting that.

Kidney Transplant
At some point, Marty's friend, Keith, went into kidney failure. As he was HIV+, nothing could be done to treat him except dialysis until a new law went into effect allowing him to receive a kidney from an HIV+ donor. Marty was a good math, so they set up for Marty to donate his kidney. However, upon hearing the potential risks to the donor, Marty briefly backed out, unbeknownst to Keith. One he saw Keith's reaction and how good a friend he was, Marty decided that he was willing to go through with it despite the risks to himself. The kidney was successfully donated.

Romantic
Keith mentioned that Marty has had many wonderful boyfriends, but isn't willing to commit.

Keith Kalber
Marty and Keith have been friends for a long time. When Keith needed a kidney transplant, Marty donated his.

Notes and Trivia

 * Keith was with Marty when he was diagnosed with HIV.