  Predicting the shape of grain boundaries is essential to control results of
the growth of large graphene crystals. A global energy minimum search
predicting the most stable final structure contradicts experimental
observations. Here we present Monte Carlo simulation of kinetic formation of
grain boundaries (GB) in graphene during collision of two growing graphene
flakes. Analysis of the resulting GBs for the full range of misorientation
angles $\alpha$ allowed us to identify a hidden (from post facto analysis such
as microscopy) degree of freedom - the edge misorientation angle $\beta$. Edge
misorientation characterizes initial structure rather than final structure and
therefore provides more information about growth conditions. Use of $\beta$
enabled us to explain disagreements between the experimental observations and
theoretical work. Finally, we report an analysis of an interesting special case
of zero-tilt GBs for which structure is determined by two variables describing
the relative shift of initial islands. We thereby present analysis of the full
range of tilt GB ( $\beta\neq$ 0) and translational GB ( $\beta$ = 0). Based on
our findings we propose strategies of controlling the GB morphology in
experiments, which paves the way to a better control over graphene structure
and properties for advanced applications.
