Must elders have more than one child?
"one who rules his own house well, having his children in submission with all reverence" (I Timothy 3:4).
"if a man is blameless, the husband of one wife, having faithful children not accused of dissipation or insubordination" (Titus 1:6).
The Greek word in both I Timothy 3:4 and in Titus 1:6 is tekna. Grammatically, it is a plural nominative / accusitive noun. A plural noun means that more than one exists. There is another form of this same word which indicates one or more and that is the word teknon, which is the base word.
In Greek, when a plural object is combined with a plural subject, we can be discussing one or more objects per subject. For example, if Bill has a daughter and Jack has a son, it would be proper to say that the men had children. Each man has a single child, but subject "men" indicates more than one man and there is more than one child being assigned to the men. This is well illustrated in I Timothy 3:12 were it mentions deacons must have children. The phrasing allows a deacon to have one or more children.
When a singular subject is combined with a plural object, the general rule is that more than one object is under consideration. This is what we have in I Timothy 3:4 and Titus 1:6.
However, there is a exception to this rule, called "plural of class." A class is a singular noun being used to represent a class of things. So, even though it is singular, it is being used to represent a plurality. Remember that this is an exception to the general rule. It is not commonly done in Greek. In I Timothy 5:4 we have an example of this exception. "Widow" is singular, but "children" is plural (tekna). We know this is a plural of class exception because within the context of the discussion, Paul talks about the responsibility of a child to his parent (I Timothy 5:8, 16). Also, Pauls says "if any widow" which means we are talking about a group of widows, considered one at a time. In addition, in the qualifications for a widow to be taken care of by a congregation Paul said, "if she has brought up children" (I Timothy 5:10). In this passage, a compound Greek word is being used that includes the word teknon which is the singular form of "children," i.e. allowing one or more. Therefore, we know that tekna in I Timothy 5:4 is one or more because of the context and it is allowable in Greek because of the "plural of class" exception.
This then leads to the question: Are I Timothy 3:4 and Titus 1:6 also "plural of class" exceptions? The blunt answer is that there is nothing in the context indicating a set of people being considered one at a time. There is nothing in the context of the passage to indicate that some elders can have only one child. The general rule of interpretation is to go with the simpliest meaning first unless something indicates we need to dig deeper. Since there is no indication that these passages are exceptions, it would be improper to claim them to be exceptions just because we might like that result.
In addition, if Paul wanted to indicate two or more children per elder, the way he phrased it is the only way possible in Greek. But if he wanted to say one or more children, he could have worded it as he did the qualification of deacons by saying "elders' children," i.e. plural with plural.
Finally, does the requirement of having more than one child make sense? The answer is "yes." The purpose of requiring children is to demonstrate the ability to manage the church (I Timothy 3:5). As parents of multiple children will tell you, no two children are alike. Just because you are successful in raising one child doesn't mean you can handle a variety of children. It makes sense that an elder demonstrate his ability to handle a variety of personalities in his household because he will have to do so in the church.
Therefore, if someone wants to claim that elders can have only one child, the burden of proof is on their shoulders. I Timothy 3:4 and Titus 1:6 contain the possible inference that one child might be allowed, but the two verses do not require this interpretation. In other words, it is not a necessary inference. Two become a necessary conclusion, some additional evidence must be presented that indicates God's acceptance of elders with only one child. I know of none.