Romans 12:15

“Rejoice with those who rejoice, and weep with those who weep.”

2 Timothy 1:4

“longing to see you, even as I recall your tears, so that I may be filled with joy.” 

What role does emotional interest and care play in developing true brotherhood?

True brotherhood / sisterhood is deepened when you show your friend emotional interest and care. By caring and even sacrificing time for a friend, friendship will grow.