The Catechism (240-242) states,
"Jesus revealed that God is Father in an unheard-of sense: He is Father not only in being Creator, He is eternally Father in Relation to his only Son, who is eternally Son only in relation to his Father."

The apostles confess Jesus to be the Word.

The Church confessed at the first ecumenical council at Nicaea that the son is "consubstantial" with the Father.

The second ecumenical council at Constantinople in 381, kept this expression in its formulation of the Nicene Creed.

The Catechism on Revelation about God the Son