TSQL, counting pairs of values in a table

Given a table in the format of

ID   Forename    Surname
1    John        Doe
2    Jane        Doe
3    Bob         Smith
4    John        Doe

How would you go about getting the output

Forename  Surname  Count
John      Doe      2
Jane      Doe      1
Bob       Smith    1

For a single column I would just use count, but am unsure how to apply that for multiple ones.