Luke
Usually, when he didn't understand something, he could find a logical, scientific reason or solution to the problem. Females, however, rarely seemed to fit any predefined construct. He could confidently tackle any problem set or experiment, but when it came to the women in his life, he felt completely and totally helpless. Especially when they cried.
His mother's tears always unsettled him, and he would wonder what he could say to make her feel better that wouldn't sound like a mere platitude. His sister cried with almost alarming frequency, as seemed to fit the pattern of many teenage girls. But when she really cried, like when she was sick, when Judith died, or when Adam had broken her heart, he found that knowing there was nothing he could say was worse than wondering what the right thing would be.
And then there was Grace, who had built up around herself virtual walls with the density of lead. All he ever wanted was for her to let him in. It started with an IM of a revelation he'd never expected. He'd held her while she cried but knew that once again, there was nothing he could say to make it better.