“ The Church is a "communion of saints": this expression refers first to the "holy things" (sancta), above all the Eucharist, by which "the unity of believers, who form one body in Christ, is both represented and brought about.”<br/><br/>
“The term "communion of saints" refers also to the communion of "holy persons" (sancti) in Christ who "died for all," so that what each one does or suffers in and for Christ bears fruit for all.”
"We believe in the communion of all the faithful of Christ, those who are pilgrims on earth, the dead who are being purified, and the blessed in heaven, all together forming one Church; and we believe that in this communion, the merciful love of God and his saints is always [attentive] to our prayers.” (Catechism of the Catholic Church 960-962).<br/><br/>
"In full consciousness of this communion of the whole Mystical Body of Jesus Christ, the Church in its pilgrim members, from the very earliest days of the Christian religion, has honored with great respect the memory of the dead; ‘Thus he made atonement for the dead that they might be freed from this sin.’” (2 Maccabees 12:46)”  
(Lumen Gentium 50)<br/><br/>
"For if we continue to love one another and to join in praising the Most Holy Trinity—all of us who are sons of God and form one family in Christ—we will be faithful to the deepest vocation of the Church." (Lumen Gentium 51)<br/><br/>
Traditionally in the Church we pray for the deceased brothers and sisters, specifically for souls in purgatory every year in November. They definitely need our prayers and our intercessions.<br/><br/>
St. John Chrysostom said: “Let us help and cherish the memory of souls in purgatory. If Job's sons obtained purification because of their father's sacrifice, then why do we doubt that offering for the deceased will not bring them comfort? We should not hesitate to help the deceased and offer our prayers to them. " (Homily on First Corinthians)