Stuff:

"XV. Bearn
...

Sous-Lieutenans.
...

Edouard Legras, ch. [i. e. la companie des chasseurs]
...."

From the Etat militaire de France, pour l'année 1787. p. 168:

http://books.google.com/books?id=T_9AAAAAcAAJ&pg=PA168

1783 ed Edouard and brother both in same company (Note 'dispositions' on p 19):

http://books.google.com/books?id=-nlotx-ev9oC&pg=PA166
http://books.google.com/books?id=-nlotx-ev9oC&pg=PA19

In 1791 he is a lieutenant and his brother a capitain (pp 438-439):

http://books.google.com/books?id=uYrx81hMq9QC&pg=PA438

"M. le baron Legras, aide-de-camp de S. A. R. le prinre de Condé, et M. Legras de Bereaguy, ci-devant préfet à Magdebourg." footnote, p 355:

http://books.google.com/books?id=pfwTAAAAQAAJ&pg=PA355

Baron Legras would appear to be a different person:
http://books.google.com/books?id=-nlotx-ev9oC&pg=RA6-PA405

1789: "Jean-Joseph le chevalier Legras, chevalier, capitaine au régiment de Béarn, chevalier de l'ordre de Saint-Lazare."
http://books.google.com/books?id=wHw4AAAAMAAJ&pg=RA1-PA167