You can name anyone you want.
Most certainly.
The best man is generally the groom's best friend or even a brother. There are no specific rules. If the wedding was taking place in another town or country and the groom did not have a best friend or brother present then he could have his bride's brother be best man or one of her male friends.
his brother jess
Prince William's best man is his younger brother, Prince Harry.
his brother prince harry!
Kevin, Kate's older brother
Brother Man was created in 1954.
the man's brother-in-law
Brother Man has 191 pages.
The Best Man at the Royal Wedding of Prince William & Kate Middleton was Prince Harry, Prince William's brother.
Edward Cullen, Bella's vampire partner, wants his brother Emmett Cullen to be the best man at their wedding in the Twilight series.
proto man
That man is your brother.