  A systematic study of fractional revival at two sites in $XX$ quantum spin
chains is presented and analytic models with this phenomenon are exhibited. The
generic models have two essential parameters and a revival time that does not
depend on the length of the chain. They are obtained by combining two basic
ways of realizing fractional revival in a spin chain each bringing one
parameter. The first proceeds through isospectral deformations of spin chains
with perfect state transfer. The second arises from the recurrence coefficients
of the para-Krawtchouk polynomials with a bi-lattice orthogonality grid. It
corresponds to an analytic model previously identified that can possess perfect
state transfer in addition to fractional revival.
