Romans 8:17
And if children, then heirs; heirs of God, and joint-heirs with Christ; if so be that we suffer with him, that we may be also glorified together.
What do you mean by relationship? We have the same father. The children of Israel all had one father, Jacob but different mothers. Did that make them not brothers?
Yes
Matthew 12:50
For whosoever shall do the will of my Father which is in heaven, the same is my brother, and sister, and mother.
Jacobs's children did not all have the same mother, did they? Yet they were all brothers.
Romans 8:17
And if children, then heirs; heirs of God, and joint-heirs with Christ; if so be that we suffer with him, that we may be also glorified together.