A composite of two pictures. Both shot with the same gear and settings.
Camera: Fujifilm X-T2
Lens: Fujinon XF90mm F2 R LM WR
Shutter speed: 1/250s
Flash: Jinbei HD-610 HSS
Reflectors below breast of dogs and from the left.
Composite done in Photshop. Added a texture to make it look a bit more painterly. For on how to add a texture, see the article "Faking a High End Portrait Backdrop With Texture Overlays" here on Fstoppers.
The father is a Mechelaar and the son a Mechelaar/German shepherd cross.