https://www.cyclescheme.co.uk/community/featured/cycling-and-the-law#:~:text=Rule%2068%20says%20%E2%80%9CYou%20MUST,footrests%20and%20a%20passenger%20handlebar.
"9. You can carry passengers… sometimes
Rule 68 says “You MUST NOT carry a passenger unless your cycle has been built or adapted to carry one”. Quite how the bike is “built or adapted” is not specified. A childseat is fine, as is a longtail cargo bike with footrests and a passenger handlebar. But you’re not allowed to give your mate a “backy” on a normal bike."
Never heard of the expression "backy" before today.
So, no two on a bike.
Have to say, just going by the reports I've seen, whatever the boys were being followed for, and it appears to be for a legitimate reason. Since they shook off the cops by cycling through bollards the car couldn't go through, the boys were then responsible for their own actions and the consequences of those actions. If they were distracted due to trying to get away, again they had caused themselves to be in that situation. They could have opted to stop an ask the cops what was up but they chose otherwise.
It's a sad incident in any case, but from here on the legal system will hopefully come to the right interpretation this time.