British Lion Williams lost his own mum Julie to a lengthy battle with cancer in 2005 while younger brother Craig also died of the disease a decade ago.
And the veteran flanker has praised Cardiff Blues colleague Davies for the way he has dealt with his own personal tragedy ahead of the Test clash in the Welsh capital.
Williams said: "We have all supported him but I can't speak highly enough of Bradley.He is only 23 but he's shown he has an old head on young shoulders - he has not let it affect him in any shape or form on the training pitch.
"There is no doubt that it will be emotional for him when he runs out and then the anthem starts.I've been in Bradley's position before but he has been awesome this week.
"He had a couple of days off but from experience playing does take your mind off things and the sooner he came back in the better. It gives you something to focus on and I'm sure it will give his family a bit of rest as well. I hope Friday night will do that for them.
"Bradley had a couple of days off but now he has a job to do in the second row with the line-out. I'm sure he will be switched on and concentrated on the job in hand."
Williams will become only the eight player - and the first Welshman in championship history to reach 50 appearances against Les Bleus.
And the evergreen star, who will also equal Colin Charvis as Wales' most-capped forward on 94 caps at the Millennium Stadium, admits it will be a special occasion.
Williams, 34, added: "It's a nice achievement and milestone to reach. I did fear I would not play in the championship after receiving some criticism of late from Warren Gatland.
"But you have to take it on the chin at international level and respond in the right way on the field. I'm happy to get the call again and I want to put in a good performance."
Championship 50-cap club
1. Mike Gibson (Ireland) 56 games
2. Jason Leonard (England) 54
3. Willie John McBride (Ireland) 53
4. John Hayes (Ireland) 51
5. Philippe Sella (France) 50
6. Rory Underwood (England) 50
7. Chris Paterson (Scotland) 50
8. Martyn Williams (Wales) 50 v France