Connective tissue is known to provide structural and functional “glue” properties to other tissues. It contains cellular and molecular components that are arranged in several dynamic organizations. One of the most relevant structural components of connective tissue is elastic fibers, whose main basic molecular components are fibrillin-1 and elastin. Two rare genetic diseases are caused by dysfunctions of both: Marfan syndrome (MFS; fibrillin-1 haploinsufficiency or dominant negative) and Williams-Beuren syndrome (WBS; elastin haploinsufficiency). Despite both being essential and tightly coupled for the assembly of elastic fibers and/or laminae, their respective resulting cardiovascular dysfunctions are opposed: the formation of aortic aneurysm, dissection, and rupture, characteristic of MFS, and aortic stenosis and cardiac hypertrophy in WBS. In both diseases, redox stress has been variably involved in their respective cardiovascular injury, however, information about the molecular machinery involved is still incomplete. In this review, we will focus mainly on the role of NADPH oxidase family members, which are better studied in the context of MFS aortopathy. We will discuss how the redox stress machinery could be differently involved in these opposed cardiovascular diseases.