  We investigate entanglement dynamics of bipartite as well multipartite
systems beyond Markov approximation. We study two pairs of cavity-reservoir
systems, modeled as four qubits and track the change of entanglement among
cavity-cavity qubits, reservoir-reservoir qubits, and also for genuine
entanglement of all four qubits. For cavity-cavity qubits, we find that
non-Markovianity prolongs the life of entanglement besides collapse/revival
phenomenon. For reservoir-reservoir qubits, entanglement sudden birth is
delayed accordingly along with oscillations. For all four qubits, with a
specific initial state, we find that genuine entanglement develops gradually,
reaches to a maximum constant value and then freezes at this value for some
time before decaying. This sudden change in dynamics of genuine entanglement
occurs for a time window where neither cavities nor reservoirs are entangled.
In contrast to Markov process, sudden change phenomenon may be recurrent in
non-Markovian regime.
