What was the relationship between Simeon and Anna?
While Simeon was holding the child in his arms, Anna came. Both of them praised God for Jesus in the Temple. Luke 2:28, 38
What the Bible says
Luke 2:28
He also took him into his arms, and blessed God, and said:
Luke 2:38
Now she, at the same hour, coming in, confessed to the Lord; and spoke of him to all that looked for the redemption of Israel.
Douay-Rheims Bible (Challoner revision), public domain.
What the Church teaches
With Simeon and Anna, the Catechism says, all the expectation of Israel comes to meet its Savior.
Catechism 529 · Catechism of the Catholic Church