Star
How could the death of one compare to the deaths of billions?
As a Jedi, he knew that they could not. The destruction of an entire star system resulting in the murder of countless individuals could not be compared to one loss. As a Jedi, he knew that.
So then why did the one hurt so much more?
The destruction of the Hosnian system shook him to the core. Had knocked the wind out of him, causing him to fall to his knees as he struggled to breathe under the weight of so much death. Was this what Obi-Wan felt when Alderaan was destroyed?
And then, hardly a day later, a light was extinguished.
Han had always shone like a star. Since they'd met (could it really have been thirty-four years ago?), Han's presence had burned bright and intense in Luke's awareness. Never waning, even in the darkest of times; at his most vulnerable. Han's light never faltered, shining fiercely and stubbornly. Since he was nineteen-years-old, that light had been a constant.
Until it was gone. Extinguished in the darkness of his failure.
It was selfish. To mourn the death of one so much more potently, to feel it not only with his senses but with his very soul. Life was fleeting. He should not dwell on such things.
But Luke Skywalker had always felt deeply and intensely. Perhaps that is why he failed so miserably with Ben. Perhaps his love for his nephew was the reason he could not properly train him. He would never know for sure.
Han's presence was wiped away, burned out of Luke's awareness, leaving a pit of anguish and grief. Not just his own, but his sister's. Another loss to add to her already great burden.
It was selfish. Indulgent. Un-Jedi like. But in spite of all that, Luke mourned.
He mourned the loss of his dearest friend, a brother in every sense of the word.
He mourned the loss of Leia's anchor; her soulmate.
He mourned the loss of his chance to say he was sorry, so sorry for everything.
Luke mourned the boy who died with him.
For when Han Solo's light was extinguished, Ben was lost, too.