In chapter four, Greg Mortenson talks about how when he was three months old his parents moved to Tanzania. While in Tanzania, his mother, Jerene, gave birth to his other siblings, the youngest one named Christa. Greg talks a little bit about how much Christa meant to him. On page 37, Relin says, "A still-growing Greg become a looming presence over anyone who would consider teasing his little sister."
I think this quote is pretty powerful because it shows that Greg was willing to stop anybody from harassing Christa. The quote really shows how much he cares for her. In the earlier chapters, Greg was going to put her necklace at the top when and if he summited. The quote also shows how much of a caring person Greg is.