A novel AB(2) nionomer, bis(4-(but-3-enyl)phenyl)methylsilane, 1a, and its analogue AB structure 1b were synthesized and polymerized with Karstedt's, Speier's, and a Pt-NHC catalyst to obtain hyperbranched and linear polycarbosilanes. Only the Pt-NHC complex afforded a regioselective hydrosilylation reaction. As a consequence, this led to a uniform polymer microstructure and at the same time to significantly increased molecular weights. Functionalization of the remaining double bonds in the obtained polymer was achieved by two exemplary routes. Hydrosilylation with a functional silane yielded chloromethylsilyl capped polymers, hydroboration and subsequent oxidation led to hydroxy-terminated polymers.