When encountering a family of parent(s) and children, always consider the possibility that the children are not full biological siblings. Some children could have been from previous relationships either parent had and others could be theirs together. Even if there were no divorces or separations, previous spouses could have either abandoned their family or died. Left with children to support, remarriage was relatively common especially if the remaining parent’s economic status made it necessary.
Never assume that what appears to be a “husband wife and their children” actually is. It may not be.