Where does the Knight fit in?

For a detailed look at each of these characters, simply follow the link provided below to access Gradesaver's summary of the prologue. In this summary, you will find the order (from highest to lowest) or status of each of the pilgrims. I assume that this is what your question refers to as far as "fitting in." Chaucer's pilgrims represent the different rungs of English society. The summary will supply you with this information in order of importance. 

The Knight is described first, as befits a 'worthy man' of high status. The Knight has fought in the Crusades in numerous countries, and always been honored for his worthiness and courtesy. Everywhere he went, the narrator tells us, he had a 'sovereyn prys' (which could mean either an 'outstanding reputation', or a price on his head for the fighting he has done). The Knight is dressed in a 'fustian' tunic, made of coarse cloth, which is stained by the rust from his coat of chainmail.

The Knight brings with him his son, The Squire, a lover and a lusty bachelor, only twenty years old. The Squire cuts a rather effeminate figure, his clothes embroidered with red and white flowers, and he is constantly singing or playing the flute. He is the only pilgrim (other than, of course, Chaucer himself) who explicitly has literary ambitions: he 'koude songes make and wel endite' (line 95).