No not at all, though they will eventually get to be large holly trees.

I was worried that it might compromise the tree's roots...

I wouldn't have thought so, they will all sort themselves out. But if you are really concerned remove them.

I'd take them out immediately, while you still can - these self set plain green seedlings grow into 25 feet high monsters...

Ah but we love our monsters Bamboo :-)

...thanks for this, I do like them really, especially as they arrived naturally, they even give me berries!

Lucky you - you've got a male and a female then... or two females and a male nearby.