One of the ministries that Graceworks has been committed to is equipping churches to mentor their young adults. These requests came because many churches were losing their young adults and wanted help to connect with them in such a way that helped them to navigate emerging adulthood and therefore provide needed help in this crucial chapter of life. This in turn helped the young adults to find their place in the church.
After some years of doing this, we came to the realisation that not only did we need to help older adults understand and help the young, we also needed the young to understand and help the older members of the church. This was the first step in what became our generations project, our research into how Singaporean Christians of five generations, namely the Silent, Boomer, Gen X, Millennial, and Gen Z, viewed the faith and the church. With greater awareness of the culture of the different generations, we could then relook at how we did young-adult mentoring.
We realised that young-adult mentoring was a concrete way to help Christians of different generations get close and personal with each other. It's one thing to know some theory of how a certain generation needs to be approached. It's quite another to share life stories with someone of a different generation. And because the different generations had different strengths and different smarts, young-adult mentoring is a mutual experience where young and old learn from each other.
Perhaps it is time to rename what we have termed “young-adult mentoring”. Maybe we should now call it “co-mentoring”.

. . .where older and younger mentor each other. . . Co-mentoring also captures the essence of mutuality and reciprocity. (Holly Catterton Allen, Christine Lawton & Cory L. Seibel, Intergenerational Christian Formation 2nd Ed. [Downers Grove, IL: InterVarsity Press, 2023], 49).

Mutuality and reciprocity are two key values of any church trying to be intergenerational because it implies:

. . . that there is a balanced give and take, that is, a sense that what we have to offer each other is of similar weight and importance. (Intergenerational Christian Formation, 20.)

Another name for co-mentoring is reciprocal mentoring:

In reciprocal mentoring, sometimes known as “co-mentoring”, two people work together through a mentoring process in which they both take on the roles of Mentor and Mentee. This could be done by each participating in both roles, or by each person taking a primary role as Mentor or Mentee, but being willing to exchange roles from time to time.
In the developmental model of mentoring, Mentor and Mentee both enter the relationship with an expectation they will be changed by and learn from the experience. To some extent, reciprocal mentoring often happens naturally in a strong mentoring alliance. As mentoring relationships progress, it is not unusual for pairs to report that at times, the Mentee takes on the mentoring role.

Those who are used to a more traditional understanding will find this reciprocity strange because mentoring is usually understood as someone older and more mature guiding the development of someone younger and less experienced. What can the older learn from the younger?
Our generations project has shown that the different generations have been shaped by different formative forces and therefore have developed different strengths. For one, the younger have much more learned expertise. They grew up in a time of a rapid growth of knowledge and have learned how to learn and assimilate large amounts of information. The older ones who have lived longer have experienced more of life and therefore have more lived experience.
Hence, young and old have much to offer each other. So, if an older adult chooses to mentor a younger adult it is with the understanding that the mentoring journey is one that is for the older adult’s growth as well. And hence we may have to move beyond the title “young-adult mentoring”.
Mentoring has always been a synergistic exercise needing the contribution of both mentor and mentee that results in blessings for both. Sharon Daloz Parks puts it well:

No matter what the mentor may offer in various forms of recognition, support, challenge, and inspiration, in the alchemy of mentoring the talents, smarts, skills, and best intuitions of the protege combine with the mentor’s wisdom to forge new realities that neither could create alone. Although initially either may seek out the other, the relationship comes about finally, through mutual attraction towards similar aims. When the relationship works, the meaning and satisfaction that it yields are gifts to both the protege and the mentor. (Sharon Daloz Parks, Big Questions Worthy Dreams [San Francisco, CA: John Wiley & Sons, 2000], 133.)

Therefore, the fact that both mentor and mentee learn and grow from the mentoring journey is not something new.
There are many types of mentoring that are needed. More basic concerns for the discipling of new believers may indeed see someone more mature in the faith guiding a new brother or sister in Christ. Even then I would argue that the more mature Christian can learn from the newer one.
Perhaps co-mentoring is the realisation that Jesus is the primary mentor and young and old are both shaped by Him through each other. Paul asks his disciples to follow his example as he follows the example of Christ (1 Corinthians 11:1). Young and old can help each other do that.