For the same reasons all other cultures do - to congratulate the new bride and groom.
Hanukkah is a Jewish celebration:http://judaism.answers.com/jewish-holidays/hanukkah
Yes
People who celebrate Kwanzaa are African American.
Jewish New Year
In their homes.
Jewish people
Jewish people who live in England celebrate Hanukkah.
Yes, most Jewish people celebrate Hanukkah.
Most Christians. People who are not Christians have other traditions.
Yes, since Hanukkah is a Jewish holiday.
they dance and eat cake
no jewish people do