My friend has 2 pedagrees difarant ages boy @girl thay have the same mum but diffarant dads @she wants 2 no if it would be ok 2 breed them after all health checks. thanks

Not without knowing all the other dogs in the pedigrees for at least 5 generations.

Unless they've been independently assessed as being superb examples of the breed, I'd say no, that's too close. All your friend will do is firmly fix any mutual short-comings.

Are these your own two white boxers? If so, no they should never be bred from, and certainly not to each other. The likelihood of having puppies with incurable hereditary problems is immense.

It is my thinking that these are your own dogs and not your friends. Unfortunately, it is also my thinking, that from the posts you have put on here, no amount of advice we give is going to make any difference. No doubt someone will (eventually) come along and say what you want to hear, and that will be the singular advice you follow.

By which time a litter of inbred handicapped puppies will have been born. :(

I personally wouldn't if your friend doesn't know what they are doing.  breeding this close is something not to be taken lightly.  Even if both are excellent doubling up can be a risky job unless lines are known VERY well! :)

Close linebreeding or inbreeding should only be done by experts who know their dogs and the last 5 generations behind them to every last detail.
I once met a GSD bred from 2 close relatves...the dog was a reasonable looking GSD with legs about 6 inches long!!!
Don't do it!!
Archer