Titus 1:6 New International Version (NIV)
An elder must be blameless, faithful to his wife, a man whose children believe[a] and are not open to the charge of being wild and disobedient.
1 Timothy 3:4New International Version (NIV)
He must manage his own family well and see that his children obey him, and he must do so in a manner worthy of full[a] respect
Many of Jesus apostles were not married and did not have children,obviously it is not necessary for an overseer to have children , however if they did have, their children had to be obedient and of full respect.
The entire congregational arrangement, with its apostles, prophets, evangelizers, shepherds, and teachers, served to produce mature Christians, spiritual adults. (Eph 4:11-14; compare Col 1:28, 29; 4:12, 13.) Obviously, then, those serving as shepherds and teachers had to be spiritually mature persons, not babes. However, more than spiritual adulthood was required of one appointed as an overseer or a ministerial servant. (1Ti 3:1-9, 12, 13; Tit 1:5-9) For example, one of the requirements for an overseer was that he be “a man presiding over his own household in a fine manner, having children in subjection with all seriousness.” (1Ti 3:4) Thus, a man could be mature in certain respects from a spiritual viewpoint, and yet, if his children were rebellious and uncontrollable, he would not qualify for the position of overseer.