A photographer can lie easily, but I don't think it is correct to say that a photograph is always lying. A photograph offers a perspective. That perspective may add truth to the (historical) reality, or it may take away from it.
The suggestion that two different family photographs need to be reconciled treats reality like it is black and white. Reality is more like a color wheel. You may see primarily blue, me pink, but we're both seeing different aspects of the same truth.
Please understand this is very different than subjectivism, or the idea that the truth is individual and our own. This is what I was trying to get at before when talking about a standard of art. There is truth and beauty and good art but it is very complex and multi-faceted and none of us see all of it.
We tend to fall into two ditches, either truth and beauty is black and white or truth and beauty is in the eye of the beholder/unknowable. Truth is neither.