However not wanting to discourage the boys' passion, they have offered to pay for passes to fish in safer waters and hundreds shared an appeal to find them.
"When we were younger, we did the same," secretary Michelle Tuffley said.
"We want children to be fishing," she added. "Especially with the summer holidays coming up."
She said it was unusual to see younger fishers at the Tardebigge reservoir and that the two boys had been "very persistent".
In a Facebook post, the group emphasised the boys were not in trouble for fishing at the reservoir.
Because the reservoir is 40ft (12m) deep, Ms Tuffley said there had to be an age limit and she hoped the boys could find other nearby alternatives.
The group has offered them free Birmingham Anglers Association passes and advice on places where they can fish safely.
More than 100 people have shared their appeal to find the boys and their families so they can offer them the passes, with dozens praising the group's actions.
The post has also inspired others to help, with offers to send the aspiring fishermen tackle to pursue their hobby.