I actually have a fairly involved backstory for Enjolras' parents--mom was from a minor offshoot of a noble family, dad was a Napoleonic soldier. Her family were émigrés who fled to the Austrian Empire during the Revolution, not that that prevented their sixteen-year-old daughter from eloping with a common soldier when the French army occupied Vienna on the eve of the Battle of Austerlitz. (Which means, yes, Enjolras' mother was born in 1789. If Hugo can pull that kind of shit with his dates, dammit so can I.) It's, um, a high-tension family, to say the least. Helped along by the fact that his parents aren't very nice people.
Fun genealogical facts: when I say 'a minor offshoot of a noble family,' what I actually mean is that Enjolras is distantly related to Lucien de Rubempré, which I'm sure would horrify both of them.
[Dieu] entend ta voix, ô fille des hommes! aussi bien que celle des constellations; car rien n'est petit pour celui devant lequel rien n'est grand.
- George Sand, Les sept cordes de la lyre