Setting up Screen Time for Family Sharing

I have set up family sharing with my two children, when I look at Family Sharing (in Settings), the two children are there. Then there are the shared features to select from. When I go to Screen Time to set this up as part of Family Sharing, the Screen Time screen is simply blank, there is nothing to be seen. I have seen this feature on friends phone and they can set up limits for their children's screen time, but not me. I simply have no options available. Any ideas? I have powered off my phone and restarted, no change. I have not tried resetting my phone.