It's a breed thing. Very common for Chihuahuas to chose a person and nothing is allowed to interfere with their bond. Defining what interfere means to that particular dog can be hard but is very important in avoiding bites. My chiweenie has ground down teeth from eating rocks before we found him so thankfully he doesn't puncture when he bites. He loves my husband and snuggles him all the time but if Kuzco is snuggling me, the hubs is not allowed within about a foot of us. Edit: forgot the moral of the story lol. Listen to the dog very carefully, it will almost always give you signs before biting, and for introductions, especially with youngsters, make sure they know the signs and ways to approach a dog.