Since the New Testament does not address this concern specifically, one must attempt to draw a reasonable conclusion based upon the evidence available.
My personal view is that the defection of an adult son, in the circumstances you describe, does not necessarily disqualify the brother from serving as an elder. My reasons for this judgment are as follows:
Every human being has been granted the responsibility of exercising his personal power of choice in the decisions of his life (Joshua 24:15; Isaiah 7:15; John 5:40; Revelation 22:17). The elder may have raised his children in the ways of the Lord, but then later, when the child was on his own, events transpired wherein the offspring made the individual decision to abandon faithful service.
Parents cannot be held responsible perpetually for the transgressions of their children (cf. Isaiah 1:2). We have discussed this principle in another article, to which we refer the reader (Will a Properly-Trained Child Never Go Wrong?).
The Qualification Considered
Paul’s admonition regarding the elder is that he must be one who “rules well his own house” (1 Timothy 3:4).
When does a child cease to be a member of his father’s house and become responsible for his own house?
It would seem to me that when an offspring moves out of his parents’ home and establishes his own independent home, that he is no longer under the control of his father and mother and they, therefore, cannot be held responsible for his conduct — as much as they may disagree with his mode of life.
Not even the sin of a youngster “under his father’s roof” would necessarily disqualify an elder. Every young person is guilty of sin.
Is the Father’s House Out of Control?
The issue is this. Does the father exercise general control over the child? Can the youthful transgressor be brought to repentance?
It’s not reasonable to expect that the elder’s home will be absolutely free from the common problems that all Christians experience in rearing children.
The elder is to be one “having [
echon — a present tense form suggesting a consistent state] believing children” (Titus 1:6) who are subject to his “rule” (1 Timothy 3:4).
If the elder’s children, i.e., those under his immediate control, are habitually disorderly and he cannot, as a general practice, “rule” (
proistemi — “to stand before” in the sense of “lead”) them, but, to the contrary, they are constantly guilty of outrageous conduct (Titus 1:6), he certainly would be disqualified to serve in that leadership capacity.
Totally rebellious children nullify the elder’s ability to lead the church (1 Timothy 3:5).
The Problem of Expediency
Having said all of the above, we must note this. It could be the case that an elder’s grown child, living on his own, could be guilty of such notorious and flagrant conduct, that it might not be expedient for the elder to continue in his role. The inordinate attention to this problem — even though he is not responsible for the wayward child’s conduct — might seriously distract him from his pastoral responsibilities, and his influence could be muted.
This need not be the case necessarily, but it could be. The judgment of the local church should be consulted in such a case.
A good elder will always put the welfare of the congregation foremost in any decision.