Got a Boston Terrier, she is 10yrs old and I have had her since she was 6 weeks. Bostons make great family pets, they are quite small in size too, but are very hard to find, you would probably have to go on a breeders list.
Also have a bull terrier who is 51/2 had since she was 8 weeks. She is the stupidest dog on the planet
Word of caution about Boxers, and I speak from experience having owned 2 years ago, they stay puppylike for years, and need quiet a lot of exercise. My oldest was 11 yrs when she died and she never really acted like an old girl.
Please be careful where you get your puppy from as there are many people out there who breed to make a fast £. Read up on different breeds and when you have a short list contact the kennel club who will send you a list of breeders.
Reputable breeders will be willing to answer any questions you have and will also ask you loads of questions to make sure you are suitable for one of their puppies.
A good breeder will also have an agreement with you that should you ever need to rehome your puppy, you will go to them first, they will help you rehome.
Whatever you do dont buy from pet shops or your local "loot" paper. Remember this puppy will be with you for the next decade or so, and so will any problems that come from bad breeding.
Sorry to ramble, but I have fostered dogs for a few years and know first hand the results of bad breeding, and impulse buying.
If you wanna rehome a homeless doggie, let me know I can point you towards some lovely people.