From the news;

New research shows that in a social network, happiness spreads
among people up to three degrees removed from one another. That means
when you feel happy, a friend of a friend of a friend has a slightly
higher likelihood of feeling happy too.

The lesson is that
taking control of your own happiness can positively affect others, says
James Fowler, co-author of the study and professor of political science
at the University of California in San Diego.

“We get this
chain reaction in happiness that I think increases the stakes in terms
of us trying to shape our own moods to make sure we have a positive
impact on people we know and love,” he said.

I have nothing much to add here, just that; In order to make your neighbors happy, tell your brother and sister that you love them.

I love you.