It would be a tough edit.
First, I would have gotten closer to the family, either physically or by lens zoom.
From the pin light in the middle of their eyes it looks like you used a hot shoe mounted flash unit with no diffuser?
Light that is on the lens axis prevents facial shadows. Facial shadows give a subjects face depth and character.
Many hot shoe flash units have a flash head that can be adjusted to match the light beam shape to the focal length of the lens and/or the subject distance from the camera.
At short focal length the beam of light is wide and subjects can't be to far from the camera.
At longer focal lengths the beam of light is made narrower as focal length increases and subjects can be further from the camera because the light is concentrated by narrowing the beam of light.
Part of the flash issue is light fall off.
Dad is furthest from the flash unit so less light got to Dad..
Inverse-square law - Wikipedia, the free encyclopedia
Small light sources deliver harsh light. Portrait photographers generally use flash that is off the camera, and that is made apparently larger by using a variety of light modifiers like umbrellas, brollys, and softboxes.