Organic silicon compound, method for producing the same, and curable composition

An organic silicon compound having an average structural formula (1):

• wherein Z represents a 2 to 20-valent group containing an organosiloxane structure, each R1 independently represents an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms, or an unsubstituted or substituted aryl group having 6 to 10 carbon atoms, each R2 independently represents an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms, or an unsubstituted or substituted aryl group having 6 to 10 carbon atoms, each R3 independently represents a hydrogen atom, an unsubstituted or substituted alkyl group having 1 to 20 carbon atoms, an unsubstituted or substituted alkoxy group having 1 to 20 carbon atoms, or an O. (oxy radical), each R4 independently represents a hydrogen atom, or an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms, each A1 independently represents a single bond, or an unsubstituted or substituted alkylene group having 1 to 20 carbon atoms, which is free of a hetero atom, each A2 independently represents a single bond, or a divalent linking group containing a hetero atom, m is a number of 1 to 3, p is a number of 1 to 10, q is a number of 1 to 10, and p+q satisfies a number of 2 to 20 corresponding to the valency number of Z.