  We prove a theorem that characterizes a large family of non-static solutions
to Einstein equations, representing, in general, spherically symmetric Type II
fluid. It is shown that the best known dynamical black hole solutions to
Einstein equations are particular cases from this family. Thus we extend a
recent work of Salgado \cite{ms} to non-static case. The spherically symmetric
static black hole solutions, for Type I fluid, are also retrieved.
