Some funny birthday cards to give to your brother can be found online on Greetingcarduniverse.com, Moonpig.com and Americangreetings.com. There is the option of sending your brother a funny e-card or printing out the card and giving it to your brother yourself.
Besides going online to find funny birthday cards for your brother, you can go into any CVS, RiteAid, Walgreens or any other drug store and then buy a card. Hallmark.com is another website that offers many humorous birthday cards for a brother. Hallmark also has stores that you can travel to in order to purchase a funny birthday card in person.