A method comprising heating in the presence of a catalyst, a mixture comprising (i) a reaction product obtained by mixing in the presence of a platinum group metal-containing catalyst at least one organohydrogensilicon compound containing at least one silicon-bonded hydrogen atom per molecule and at least one compound having at least one aliphatic unsaturation; (ii) at least one endblocker, and optionally (iii) at least one organosiloxane chosen from a hydrolyzate or a cyclosiloxane, so to cause polymerization of components (i), (ii), and optionally (iii) to form branched polymers.