My employer, Monarch, is an example of several types being flown by the same pilots. As an example my licence covers A318/319/320/321 and 330s. Technically the narrow bodies are one type and the 330 is another although there are some significant difference evan between the narrow bodies (for example are 320's have CFMs, 321's have IAE and the 330's have RR Trents for example).
In a same vein some of our pilots fly 757s and 767s.