@Cynthia334 there are a bunch of issues relevant to your situation, so it is a little complicated.
It is very common for guests to put the wrong number of guests, but it isn't always because they are trying to be sneaky. If the reservation says "1 guest" often it means the person was not aware they needed to set the number of guests (as the default is set to 1 guest if the traveler doesn't change it.)
There is no magic way to make sure the guest is setting the proper number, but you can help make sure it happens by communicating with the guest and asking questions. Some hosts ask for the names of all the guests and (if you are on-site or nearby) you can make sure that only the previously identified guests are allowed on the property.
One of the things that complicates the issue is that Airbnb does not count infants as guests. So, from the perspective of Airbnb, your guest's group is only 4 guests: the booking guest, his spouse, and the 2 teenage boys. This would make it hard for you to ask the group to leave for having too many guests, as Airbnb would view the group as numbering 4.
https://www.airbnb.com/help/article/433/can-children-travel-on-airbnb
You sort of add the topic of pets at the end. If the animal is strictly a pet, and you do not allow pets, then certainly you can disallow them from staying. Of course, there have been many discussions where hosts complain that guests will claim a pet is a "service animal", which you *cannot* disallow.
The topic of pets and service animals is a big topic itself. For more information about that, you should search this community for the discussions on service animals.