I don't know of any 'rules' about this so this may not help but....
I have the same situation with three batches of chicks 10 weeks 7 weeks and 5 weeks.
I think my age gap is too big and I will keep them separate (but in the next pen) until the youngest is about 9-10 weeks.
Then I separate the cockerels away and join the hens together - I will probably be culling the older cockerels at the same time this year.
Worked out well last year
