Who is this cardinal in this picture? Who is this pope's auxiliary? I see him with the Pope in many pictures. Thanks
The answer to your question is Mgr. Guido Marini.
Unfortunately, he is not a Cardinal or even a Bishop.

Mgr. Guido Marini is the Papal Master of Ceremonies also known as the Master of Pontifical Liturgical Celebrations. The title was once known as the Priest Assistant in the days of old.

Guido Marini (born 31 January 1965) is an Italian priest of the Catholic Church, who has been the Master of Pontifical Liturgical Ceremonies since 1 October 2007. Pope Francis has extended his appointment to 2022. He previously served as chief liturgist for the Archdiocese of Genoa.
Marini was named Master of Pontifical Liturgical Ceremonies on 1 October 2007, appointed to another five-year term by Benedict XVI, confirmed in that office by Pope Francis in April 2014, and appointed to another five-year term in 2017. Francis also named him a member of the Congregation for the Oriental Churches on 19 February 2014.
Marini, following his appointment as Master of Pontifical Liturgical Celebrations, restored some traditional elements of papal ceremonial. During his time as Master of Ceremonies the Papal Altar was rearranged. The seven candles and crucifix were placed in a line across the Altar rather than clustered on the sides. This arrangement has become known as the &quot;Benedictine arrangement&quot;.
In a January 2010 speech, Marini supported calls in the church for a &quot;reform of the reform&quot; of liturgy. He said: &quot;For some years now, several voices have been heard within church circles talking about the necessity of a new liturgical renewal,&quot; adding that a new renewal movement would be &quot;capable of operating a reform of the reform, or rather, move one more step ahead in understanding the authentic spirit of the liturgy and its celebration.&quot;
In 2015 Pope Francis made changes to the public ceremony of investiture of the pallium on metropolitan archbishops emphasizing that the investiture is an ecclesial event of the whole diocese, and not merely a juridical or ceremonial event. Marini said that from now on – starting from 29 June this year – the ceremony of investiture of the pallium will take place in the Metropolitan Archbishops' home dioceses and not in the Vatican.
During Marini's time as Master of Ceremonies Pope Benedict ceased to use the papal staff made for Paul VI and began to use an older one made for Pius XI. Due to the weight of that staff, Benedict had his own made which is much lighter, and shares a similar style with the previous one. Pope Francis occasionally makes use of this one also in order to emphasize continuity with his predecessor. He also made decisions about the use of papal vestments at Mass and other pontifical celebrations, dressing Cardinal-Deacons in dalmatics when serving pontifical celebrations.