Who you are, where you originate, how you originate, the type of relationship, how you were parented and so on, has a direct influence on how you parent and are parented. The parenting roles are diverse with birth parents, step parents, adoptive parents, foster parents, single parents, separated parents and any combination of those roles. No wonder family life can be so complex.
Unfortunately, it appears that for many people, the needs of their future and present children are the last priority when it comes to having a family. Perhaps that the great need to have a family by one or both parents outweighs any future need of the children hence the industries related to IVF, 'baby farming' and adoption. Whilst understanding the need to have a family, perhaps this isn't always thought through sufficiently well to see that the needs of the family might be different because of the way the family is created.
The parenting roles are sometimes problematic as the styles of parenting may be different between both parents causing conflict between the couple and confusion for the child. It would be no surprise to see 'acting out' behaviour from the child over these inconsistencies.
It is vital that children in a family feel safe, loved and understood by both parents and not feel that the sole outcome is control and being kept down, quiet and emotionally imprisoned. Their learning comes from, in part, from the parents role modelling acceptable behaviour. which would not include having arguments in front of their children.
Child safety is not just about potential accidents or "Stranger Danger" it is about the emotional safety that comes from sound parenting practices.