Daffy Duck and Donald Duck are both cartoon ducks. However, they are not related.
Daffy Duck is a Warner Brother character originally created for Leon Schlesinger Productions. He appeared in 130 Looney Tunes and Merrie Melodies cartoons during the golden age of animation, as well as numerous films in more recent years.
Daffy Duck’s first appearance was in Porky's Duck Hunt in 1937. The character was originally voiced by Mel Blanc.
Donald Duck is a Disney character who first appeared a few years before Daffy Duck, in the 1934 Silly Symphony cartoon the Little Wise Hen. Donald Duck was originally voiced by Clarence Nash.
Both Donald and Daffy are anthropomorphic ducks. However, Daffy is a black duck and Donald is a white Pekin duck.