I don't think having a parent who committed suicide creates a genetic risk factor that makes their child more likely to commit suicide. However the child might have a per-disposition for the disorders the parent had that maybe contributed to their suicide. The child developing the same disorders would increase their risk for suicide.

So basically if a childs parent commits suicide due to say depression, it is likely the child could get depression based on genetic risk factors and that could put them at a higher risk for suicide.