He is only seen with his sisters in the original film, comic, and books.
In between the long gap between both films, Scamp appeared in many Disney comics, including his own comic strip which ran in newspapers from 1955 to 1988.
In Lady and the Tramp II, Scamp appears to be the smallest one due to the ending where his sisters are seen to be taller than him though this might not be so as Scamp has a habit of slouching or hunching his shoulders.
Scamp has more American Cocker Spaniel in him than terrier due to a few scenes where Tramp takes the chains off him he is lighter colored, when he flops his ears down a couple of times his ears are seen to be longer than Tramp's and his fur size matches Lady's.
Scamp and Danielle are the two major gutter mouths and troublemakers in the family.