Hello! So in the English language, when the beginning of the sentence, or the subject, has more than one individual, we use the verb that does not end in "S". On the other side, if there is only one person that makes up our subject, we will use the verb that ends in "S".
In this case, we see that Mr. AND Mrs. White dwell with their son Herbert. In our instance, we will use "LIVE" because two people live with him.
Hope I was able to help!
