[toni-a]

Thanks Klaus, much appreciated. So, I’m trying to put together a lens collection to shoot family photography with a Canon R5. Which approach would you recommend? In light of your response and really helpful reviews, I was thinking about the following line up:

1. RF 50mm f1.2 L IS USM
2. RF 85mm f1.2 L IS USM
3. RF 24-105mm f4 L IS USM

The RF 50mm f1.2 and RF 85mm f1.2 would do the heavy lifting, while the RF 24-105mm f4 would give me some flexibility with focal length when necessary. Alternatively, I could remove the RF 24-105mm f4 (and perhaps the RF 50mm f1.2), and replace it with the RF 28-70mm f2 USM L. However, I wonder if the RF 28-70mm f2 will end up being too big / heavy to shoot with in practice. I’ve also shot with the RF 50mm f1.2 and really liked it. Thanks in advance for any insights / suggestions.

If all you need is family portraits then 24-105f4L should do something like 95% of your needs
Believe me, you don't need the f1.2 primes for family portraits, I opted for the 85mmf2.0 and no regrets, it is good enough for the job, it can focus closer and you can have your child's face/eyes filling the frame, something the f1.2 can't do because of longer minimal focus distance and you can do flower closeups etc something the f1.2 can't do neither, you will have to test its autofocus speed in the shop to decide if it's fast enough for you or no.
I would pass on the 50mm and opt for 35mmf2.0 it has stabilization and would give low light capacities better than the 50f1.2 being stabilized, unless you are cropping or printing on A3 paper or bigger you won't be able to spot any difference in sharpness.
Add an ultrawide or the tiny 16mmf2.8 and you have everything you need