Originally posted by: ..RamKiJanaki..
I believe Ram loved all his brothers dearly and equally, but Lakshman's place was different. He was a part of Ram, and that's why I think Ram could never survive without him nearby.
He could live even without Sita, because Mahalakshmi resides in his heart even if she's not present in her physical form, but without Sesh Naag, Hari ceases to exist.