i am confused by your question...
yes, unneutered male dogs will want to mate with any unspayed female (who is in heat) naturally, that is why it is SO IMPORTANT TO SPAY AND NEUTER. Only irresponsible pet owners would not neuter and spay their pets. Also, only irresponsible pet owners would let their unaltered pets to be near the vicinity of other unaltered dogs. if you know you have an unspayed female, you need to keep her away from other dogs when she is in heat, and any unneutered males need to wear belly bands. so, what you described about your uncle's dogs wont happen..
it is a really common misconception that mutts are "better' bc pure breds have inbreeding and thus hereditary diseases. Uh, not true! part of why there is so many misconceptions in this area is because people throw and use terms like "i have my dogs' papers" and "designer dogs" and "pure breds" too loosely and often, wrongfully.
first, pure bred dogs are healthy- if they come from a reputable breeders. A reputable breeder is someone who 1) is AKC registered 2) SHOWS THEIR DOGS and 3) conducts DNA and titer testing on all their dogs BEFORE consider using them to breed, or even enter into the breeding pool. If a breeder does not do all of the above things, then even if that person only breeds pure breed, that breed is NOT QUALITY b/c he/she is not doing anything to BETTER the breed. You are suppose to weed out undesirable traits and try to improve the health of your dogs...thats why u do tests and show your dogs. When you show, you are constantly comparing your dog to the standard of the breed, from every level. Whether it is the coat of the dog, the bone structure, the teeth, the eyes, everything is being compared for the improvement of the breed. this way, each generation will not only be healthier, but also maintain the desirable looks that represent each breed. Therefore, pure bred dogs who come from reputable SHOW BREEDERS will always be healthy. SHOW breeders do not use sick dogs to breed.
Second, "papers" are used so loosely, people think any pet shop r back yard breeders who give them "papers" are legit- NOT TRUE! first, those papers can be forged very easily. Second, AKC gives u registration bc ur pure bred, but as i explained prior, pure bred doesnt really mean quality nor healthy. Unless your "papers" come from a SHOW BREEDER, it doesnt mean anything as far as guarantee.
Designer dogs are mutts. period. mutts are not healthier, b/c u dont know who the ***** and stud are..think about it, a person who breeds a "malti poo" - so you are mixing the incliantion of liver shunts and luxtating patella of both breeds together..do you really think that is healthy??? u are combing traits of potentially really opposite breeds of dogs and creating a new dog that is hard to predict in terms of personality and genetic deformities. it is like playing Russian Roulette. I see people ask all the time about personalities, weight, health, grooming behavior of mutts..and that goes to the heart of the problem- there is no answer b/c u dont know what kind of mix/mutt you have! That is why those who cross breed dogs are irresponsible and inhumane.
force breeding is when inhumane puppy mill owners use sick or really small females to breed. these females (under 4 pounds usually) should not be bred b/c they either will have miscarriages or will need C sections to give birth. but, these humans purposely target these small females b/c they want to create mutts that are "small" so they can sell to people who go "oohh" and '"ahhh" over "teacups.' Meanwhile, these "teacups" die before they reach their 1st birthday due to liver shunts. That is called force breeding- making unqualified females breed, causing often their own deaths and birthing to unhealthy pups.
do i expect every person to buy a dog from a show breeder? NO. best route is always to adopt, neuter and spay. but, if you can not do so, and want to buy a specific breed, then please buy from a show breeder. a show breeder is like the ones we see on TV at the Westminster shows...they know their lines inside and out and when you buy from them, you know your dogs will be healthy and you are not contributing to the cycle of greed and torture from puppy mills. Show breeders often put in more money into their dogs (testing, showing) then they make money off selling dogs..i know that b/c my Mia comes from a very well known top tier Maltese breeder. Her breeder spends so much money into his dogs, and he very rarely sells his pups...or breeds them..most of the time is spent on showing. When a breeder devotes so much of his time and money into dogs, you KNOW they are doing it for passion and love, not money. That is why i support and believe in buying only from show breeders. i would also boycott from any pet supplies store that sells puppies. those are from puppy mills.