  In this paper we introduce a $\theta$-family of spacelike surfaces in the
Lorentz-Minkowski space R^4_1 based in two complex valued functions $a(w),
\mu(w)$, which when they are holomorphic we will be dealing with a family of
spacelike minimal surfaces. The $\theta$-family is such that it connects
spacelike minimal surfaces in R^3_1 to spacelike minimal surfaces in R^3. We
study the family through of the curvature and we prove that the family
preserves planar points and moreover, that the existence of planar points
corresponds to the existence of solutions of equation |a_w(w)|^2 =0. We also
show that if a pair of surfaces are associated through of a $\theta$-family
then they can not be complete surfaces. As applications we focus to one type of
graph surfaces in R^4_1 and we prove that if the imaginary part of $a(w)$ is
zero at least in a point then the surface cannot assume local representations
of that type of graph. Several explicit examples are given.
