2 cats male and female around 7 months old

Question
I have a Bengal kitten male about 7 months.  I also have a white kitten about the same age.  Not exactly sure I adopted both of them.
I know that she can go into heat at anytime now and she is starting her affectionate behavior towards me but not the male Bengal just yet.  I don't want her pregnant just yet.  I do want them to breed just once and then I am getting them both spayed and neutered.  I have homes for them already because they will be half Bengal and I want to keep one myself.   My male cat keeps trying to mount and get aggressive with her.  She seems to do well with fighting him off but its frustrating because I know its instinct for him and I keep getting upset with him.  My question is can I allow the process just to happen naturally? If I shouldn't cause of their age,  what should I do to avoid her getting pregnant so young? If I can allow it to happen naturally what are the dangers in having her pregnant at 7- 8 months.  She is not in full heat yet.  I know this because I do have animal care background but it has been 12 years since I studied.
My other question is.  If he is a little older than her, will his aggressiveness get worse?  Can she handle herself?  Is he actually hurting her  because she is not ready but he senses she is starting?  Will he hurt her?
I will get them spayed an neutered after her first litter.  Just want to make that clear so no one attacks me on that.  I understand the problem with cat population.

Answer
Hi Stefanie, that is a lot of questions so if I miss any just write me back again.
She should not be bred this young for several reasons:
-the nutrition she should be using to grow and become healthy will be going to the kittens instead of herself at a time that she still needs it for healthy teeth and bone development especially
-she is too young to care for the kittens properly. Some young moms can handle it but many will walk away from the kittens to play or do something else and then you are left raising the kittens with a bottle
-she may have problems actually delivering the kittens because she is not full size. This is not a common problem but you need to be prepared for the stress and expense of a c-section if it comes to that
Regarding what to do with them to delay the process.. well us breeders are forced to keep our cats separate. This means that one of them will need to be in a cage until they are old enough to breed. This is why I do not encourage people to breed cats that are not prepared financially and physically set up to do it. It is not an easy undertaking if you want to do it correctly, which it sounds like  you do.
Regarding her being in "full heat". Cats do not always come into full heat before being bred. When the male cats mounts her she can come into heat at that MOMENT !! I am not kidding.. I have seen it myself. A male cat can jump onto a female that is not showing signs of heat and that female will drop into position and let herself be bred.They are not like dogs that have a predictable heat cycle. You can NEVER leave an unspayed female and unneutured male together once they are over 4-5 months old without risking a breeding. The only time a female cat over 4 months old is NOT IN HEAT FOR SURE.. is when she is spayed.. or if she is pregnant.. that is it !!
Cats are always ready to be bred.. just like rabbits and that is why they are so prolific.
Your male cat will get more aggressive with her as time goes on.. until she lets him breed her.. Because  he is bengal  you do need to keep an eye on them even when  you are ready to breed them. Depending what generation (f1,f2 etc) he is, he could be quite aggressive with her and they have been known to hurt the females.
Teresa