Quote Originally Posted by Tavrobel View Post
Umm, no, Mariadoc is Frodo's second cousin (or immediate cousin, I have no access to my books and family trees at this time). Peregrin is Frodo's third cousin (or something twice removed).
http://en.wikipedia.org/wiki/Took_clan

It's not the greatest layout, but it helps with the determination of their relationship to Frodo. The Took Clan's family tree is superior to the Brandybuck's. In terms of information given.

Anyway, Merry and Pippin are first cousins to each other.