What were the ages of the Apostles Peter and John when Jesus was crucified? What were the ages of the Apostles Peter and John when Jesus was crucified?
What I’ve heard is Peter was about the same age as Jesus (30-33), while John was an older teenage, approximately 18.  This makes sense in the passages:

When Jesus saw his mother and the disciple whom he loved standing nearby, he said to his mother, “Woman, behold, your son!”  Then he said to the disciple, “Behold, your mother!” And from that hour the disciple took her to his own home.  (John 19:26–27, ESV)

A teenager along with women would be less threatened being present at the crucifixion.

Both of them were running together, but the other disciple outran Peter and reached the tomb first (John 20:4, ESV)

For men who were not athletes, you would expect an 18 year old to outrun a 30 year old.

Peter turned and saw the disciple whom Jesus loved following them, the one who also had leaned back against him during the supper and had said, “Lord, who is it that is going to betray you?”  When Peter saw him, he said to Jesus, “Lord, what about this man?” (John 21:20–21, ESV)

Jesus had told Peter to feed his sheep.  Usually younger brothers were given the task of taking care of the literal sheep.  Peter had to get used to the idea that shepherds (pastors) were elders.
What other evidence to we have for the ages of Peter and John at the crucifixion.
What were the ages of the Apostles Peter and John when Jesus was crucified?
According to Catholic tradition St. Peter was the oldest person amongst the Apostles; while St. John was the youngest apostle.

John the Apostle (6 AD– 100AD) was one of the Twelve Apostles of Jesus according to the New Testament. Generally listed as the youngest apostle, he was the son of Zebedee and Salome. His brother was James, who was another of the Twelve Apostles. The Church Fathers identify him as John the Evangelist, John of Patmos, John the Elder and the Beloved Disciple, and testify that he outlived the remaining apostles and that he was the only one to die of natural causes. The traditions of most Christian denominations have held that John the Apostle is the author of several books of the New Testament.

If St. John was born in the year 6 AD, that means St. John was about 24 years old at the time of Jesus’ crucifixion, if we take the Crucifixion as been in the year 30 AD.
The Catholic Church does not know with any exactitude the real timeline of the Apostle Peter. So much of this question is simply based on tradition.
For the most part, it is believed that the Apostle St. Peter was born in Bethsaida (John 1:42, 44), about the year 1 AD.

St. Peter's true and original name was Simon, sometimes occurring in the form Symeon. (Acts 15:14; 2 Peter 1:1). He was the son of Jona (Johannes) and was born in Bethsaida (John 1:42, 44), a town on Lake Genesareth, the position of which cannot be established with certainty, although it is usually sought at the northern end of the lake. The Apostle Andrew was his brother, and the Apostle Philip came from the same town. - St. Peter, Prince of the Apostles

As for how and when the Apostle St. Peter died, it is traditionally believed that he died between 64 and 67 AD and was crucified upside down at Rome. That makes St. Peter between 63 and 66 years old when he died. Historical documents are not more sure of anything more exact. One can read what the Catholic Encyclopedia has to say on this subject. Some even claim he died in 55 AD.
If in fact, St. Peter was born in the year 1 AD that would make St. Peter 29 years old if we hold the Crucifixion as being done in the year 30 AD.
There seems to be little historical evidence to support the ages of any of apostles and that is why the Church tends to follow tradition in this matter.