In Catholicism people pray to the saints, angels and the Virgin Mary. Is then, in Catholicism, heaven filled, besides angels, with the saints and the Virgin Mother?
Yes, there are people in heaven.
Some, who were born before Christ's resurrection are:
2 Kings 2:1-12 “And it came to pass, when the Lord would take up Elijah into heaven by a whirlwind…And fifty men of the sons of the prophets went, and stood to view afar off: and they two stood by Jordan….And it came to pass, as they still went on, and talked, that, behold, there appeared a chariot of fire, and horses of fire, and parted them both asunder; and Elijah went up by a whirlwind into heaven….And Elisha saw it, and he cried, My father, my father, the chariot of Israel, and the horsemen thereof. And he saw him no more…”
Hebrews 11:5 “By faith Enoch was translated that he should not see death; and was not found, because God had translated him: for before his translation he had this testimony, that he pleased God.”
- The Blessed Virgin Mary
CCC 966 "Finally the Immaculate Virgin, preserved free from all stain of original sin, when the course of her earthly life was finished, was taken up body and soul into heavenly glory, and exalted by the Lord as Queen over all things, so that she might be the more fully conformed to her Son, the Lord of lords and conqueror of sin and death."508 The Assumption of the Blessed Virgin is a singular participation in her Son's Resurrection and an anticipation of the resurrection of other Christians...
And probably many others.
It is a point of mild contention whether canonisation is infallible, but most theologians agree that a papal canonisation is infallible. Most notably St Thomas Aquinas (Quodlib. IX, a. 16):
Since the honor we pay the saints is in a certain sense a profession of faith, i.e., a belief in the glory of the saints, we must piously believe that in this matter also the judgment of the Church is not liable to error.
So, I would say Heaven is 'full' (although it is an immaterial place) of saints. Although not as full as Hell.
Here are some helpful resources. http://www.newadvent.org/cathen/02364b.htm - Infallibility section https://taylormarshall.com/2008/08/is-assumption-of-mary-in-bible.html https://www.catholic.com/qa/are-canonizations-infallible
Is then, according to Catholicism, heaven filled, besides angels, with the saints and the Virgin Mary?
There is still room in heaven for many more saints. I will let Blessed Catherine Emmerich answer for me through her revelations.
Man was created to fill the choirs of the fallen angels. Were it not for the Fall of Adam, the human race would have increased only till the number of the fallen angels was reached, and then the world would have come to an end. Had Adam and Eve lived to see even one sinless generation, they would not have fallen. I am certain that the world will last until the number of the fallen angels has been filled, until the wheat shall have been reaped from the chaff.
At the Fall of the angels, myriads of bad spirits descended to earth and into the air. I saw many creatures under the influence of their wrath, possessed by them in many ways. - Life of Our Lord Jesus Christ (The Creation)
We know for sure that the criminal crucified next to Jesus is in heaven, as Jesus himself told him:
Jesus answered him, "Truly I tell you, today you will be with me in paradise."
We should be sure St. Paul is in heaven too, as he declared:
Now there is in store for me the crown of righteousness, which the Lord, the righteous Judge, will award to me on that day--and not only to me, but also to all who have longed for his appearing.
The latter part of the phrase might suggest there are several other in heaven too.
Is there anyone in heaven? (Catholicism)
Yes, there is the Holy Family in Heaven, Lord Jesus Christ, the Blessed Virgin Mary and St. Joseph all went to Heaven with their souls glorified and their undefiled bodies resurrected.
- Jesus Ascends to Heaven "Now when He had spoken these things, while they watched, He was taken up, and a cloud received Him out of their sight. And while they looked steadfastly toward heaven as He went up, behold, two men stood by them in white apparel, who also said, “Men of Galilee, why do you stand gazing up into heaven? This same Jesus, who was taken up from you into heaven, will so come in like manner as you saw Him go into heaven.”(Acts1:9=11)
- Assumptions of the Blessed Virgin Mary
On 1 November 1950, in the Apostolic Constitution Munificentissimus Deus Pope Pius XII declared the Assumption of Mary as a dogma:
By the authority of our Lord Jesus Christ, of the Blessed Apostles Peter and Paul, and by our own authority, we pronounce, declare, and define it to be a divinely revealed dogma: that the Immaculate Mother of God, the ever Virgin Mary, having completed the course of her earthly life, was assumed body and soul into heavenly glory. - Assumption of Mary
- Church Approved Apparition of St.Joseph
St. Joseph also had an approved major apparition and this would mean that the homily of St. John XXIIII stating the merit of the resurrection of St. Joseph body was true. St. Joseph body was resurrected meaning when St. Joseph appeared in a visions what were seeing is a glorified body and soul like Mary and Jesus.
On May 26, 1960 Pope John XXIII in his homily for the feast of the Ascension of Our Lord made a statement that the Assumption to Saint Joseph is worthy of pious belief (). He also stated that he believed the same privilege was accorded to Saint John the Baptist33. This is the first time that a Pope has ever made a public statement on the subject and the fact should offer great reassurance to those who feel it would be contrary to their religious sentiments to imagine Christ refusing Joseph this crowning grace. Pope John's words are a guarantee that such a belief is truly prudent and therefore can no longer be classified as a "pious exaggeration". - St. Joseph: A Theological Introduction
Here's the link on the Church approved apparitions of St.Joseph;
Devotion To St Joseph’s Most Chaste Heart – Approved Apparitions…
Many know about approved apparitions of our Blessed Mother. But only a handful realize that there were apparitions in Itapiranga, Brazil from 1994-1998 in which St. Joseph appeared along with Mary and Jesus.
In January 2010, after much study, prayer, reflection, observation and seeing the growth in the faith life of thousands, the local ordinary, Bishop Carillo Gritti declared a Decree of Worship favoring the Itapiranga appearances and in an earlier document called it of “supernatural origin.” - Devotion To St Joseph’s Most Chaste Heart – Approved Apparitions
So, the Catholic Church’s devotion to the Holy Family is now complete. The Sacred Heart of Jesus, the Sorrowful & Immaculate Heart of Mary and also the Devotion to the Chaste Heart of St. Joseph.
All the souls of Saints and Martyrs are also present in Heaven and the Catholic Church commemorates their feast day on November 1.
While all the souls who completed their purification in purgatory and now enjoy the beatific vision in Heaven are commemorated by the Church every year at November 2.
In closing, Catholicism teaches that the Holy Family are there in Heaven together with all the angels, saints, martyrs and purified souls and the Catholic Church called this the Triumphant Church.