The central process through which intimacy is acquired is peer group identification mutuality among peers social support early career and child bearing choices

The answer is mutuality among peers. In addition in the young adulthood,  the responsibilities in this stage are centered in the order of the drive to found intimacy, connection, and significant peer relationships. The post persuasive and significant peer relationship is marriage, and this is also the relationship that trends toward the most depth and intimacy. As a result the resolution of the psycho-social crisis is attained by establishing intimacy (mutuality) between peers.