kayw19,
This line has been researched quite a bit.
Pierre Lajeunesse, aka/Peter Young was born and baped, 16 Jan 1848 in Iberville (St-Athanase-de-Bleury), Montreal, PQ, CN. He was the son of Henri Lajeunesse and Marguerite Terrien/Therrien.
I've taken this line back to France, there is no known "dit" surname, not that I've found, associated with this Lajeunesse line.
There are some Acadian lines which marry into this Lajeunesse, however one of the most common queries is whether there are 1st nation associations. There has been no documentation which supports 1st Nation assertions.
Some other threads discussing th same Peter Young:
http://boards.ancestry.com/surnames.lajeunesse/234/mb.ashx