marcus aemilius lepidus (triumvir)

Wiki Classical Dictionary has a nice write-up on the Triumvir Marcus Aemilius Lepidus, which helps as background for our current read, Three's Company.

More can be found in Appian (beginning here) and Cassius Dio (beginning here).

Bingley in his post below has more sources:

 52/17  the burning of the senate-house, and the attack on Lepidus' house.