This verse is part of a speech delivered by a young man being tortured for refusing to violate Jewish law in the face of pressure from King Antiochus. Let's break down the meaning:

"But he cried out and said, Know you⌃ not, that the father of those who are dead, became the father of me also..." This refers to the previous martyrs who have already been killed for their faith. The young man is claiming a spiritual kinship with them. He sees their loyalty to God, even to death, as a kind of inheritance or legacy. In other words, he considers himself a spiritual son of those who died for their faith. Their commitment has now become his.
"...and that the same mother bare me..." This is a metaphorical statement. The "mother" isn't a literal, physical mother, but rather the Jewish faith, tradition, or community. The young man is saying that he shares the same religious upbringing and heritage as those who were martyred.
"...and that I was brought up in the same tenets?" This reinforces the previous point. He was taught the same religious principles and beliefs as the others. He has the same commitment to upholding Jewish law. "Tenets" refers to the core beliefs and principles of Judaism.

In summary, the young man is asserting that he is bound to the previous martyrs by faith, upbringing, and commitment to Jewish law. He sees their sacrifice as a model and inspiration for his own resistance.

The verse is powerful because it highlights the strength and continuity of religious tradition and community. The young man isn't just an individual making a personal choice. He is part of a larger historical and spiritual lineage. He sees himself as continuing a tradition of resistance and faithfulness, even in the face of death. This helps explain his courage and conviction in refusing to compromise his faith.