It may not be what you mean by the question, but some groups look upon a "mother of the church" as a woman in a position of authority and leadership. With this in mind:
The phrase "mother(s) of the church" is not in the Bible, nor is the concept. There are, of course, mothers IN the church, and there are instructions to be found regarding, and for, older men and women both:
1 Timothy 5:1, 2 - Do not rebuke an older man, but exhort him as a father, younger men as brothers, older women as mothers, younger as sisters, with all purity.
Paul is telling Timothy to show respect for godly older men and women as one would a father and mother in exhorting them (providing instruction, correction, comfort and encouragement), but does not grant them any special position of leadership.
Titus 2:1-5 - But as for you, speak the things which are proper for sound doctrine: that the older men be sober, reverent, temperate, sound in faith, in love, in patience; the older women likewise, that they be reverent in behavior, not slanderers, not given to much wine, teachers of good things that they admonish the young women to love their husbands, to love their children, to be discreet, chaste, homemakers, good, obedient to their own husbands, that the word of God may not be blasphemed.
Note that older women are told to instruct the younger women in practical matters, not spiritual or doctrinal. Also, they are not told to instruct men, older or younger (their own children being the exception - 1 Timothy 5:10). The idea of a "mother of the church" as a spiritual leader goes beyond the practical and is not found in the Bible.