Who is Gerry?

Tom Godwin's "The Cold Equations" is the story of Marilyn Lee Cross, an eighteen-year-old stowaway on an Emergency Dispatch Ship which is delivering medical supplies to a colony on the galactic frontier. Marilyn has stowed away on the ship to visit her older brother Gerry, who lives on the colony of Woden near the southern edge of Lotus Lake:

“I wanted to see my brother. He’s with the government survey crew on Woden and I haven’t seen him for ten years, not since he left Earth to go into government survey work.”

Gerry's work on the frontier is dangerous, as the pilot makes clear:

"On Woden, for example, there are only sixteen men — sixteen men on an entire world. The exploration parties, the survey crews, the little first colonies — they’re all fighting alien environments, trying to make a way for those who will follow after. The environments fight back, and those who go first usually make mistakes only once. There is no margin of safety along the rim of the frontier; there can’t be until the way is made for the others who will come later[...]"

Gerry's pay is commensurate with the risk he takes, however, so he regularly sends money back home to his family on Earth, where their "little shop just brought in a bare living." He is due to be posted to the Mimir colony next year, and Marilyn is in fact heading to Mimir on a space cruiser herself when she learns that the EDS is going directly to Gerry's current colony. She longs to see him sooner, and so she hides on board the EDS, not understanding the fatal consequences of her choice.
Gerry clearly cherishes his baby sister: he paid for her to take a linguistics course which enabled her to get the job on Mimir. He bought her "a bracelet of fire rubies on [her] sixteenth birthday. It was beautiful — it must have cost him a month’s pay." Marilyn adores him and sees him as her friend and protector, telling the pilot how Gerry comforted her as a small child when her kitten died and how he even went to some effort to get her a new kitten the very next day, to minimize her sadness.
The pilot is able to raise Gerry on the communicator as the EDS approaches the planet, so that Marilyn can speak to her brother one last time. Gerry is horrified to learn that Marilyn has stowed away, as he knows the penalty for her actions, but his concern is purely to comfort Marilyn as much as possible in her last moments:

“Don’t cry, Marilyn.” His voice was suddenly deep and infinitely gentle, with all the pain held out of it. “Don’t cry, Sis — you mustn’t do that. It’s all right, honey — everything is all right.”