Circling back to Q's full circle/welcome back Huma post:
Muslim Brotherhood had basically no presence in Syria pre-Syria uprising in 2011. MB being the ones united with the worlds cabal of communists that are more the political/ideological wing, while ISIS represents the militant wing.
https:// en.m.wikipedia.org/wiki/Muslim_Brotherhood_of_Syria
In 2012, Brotherhood activists created the Commission for Civilian Protection (CCP). The CCP is considered to be a front for the Brotherhood,[31] tasked with helping armed units inside Syria connect with each other and with sponsors abroad. Its website lists numerous affiliated factions, distributed across Homs, Damascus, Idlib, and elsewhere; however, most of these groups are small and generally self-identify as members of the Free Syrian Army or the Syrian Islamic Liberation Front.[32] The Syrian Muslim Brotherhood is believed to control, through funding, one-fourth to one-third of the disparate armed rebel brigades known collectively as the Free Syrian Army (FSA).[12]