When families blend, shifting roles and adjustment can create tension, as everyone settles into the changes. A new stepparent may perceive that the biological parent is favoring his or her children due to concern for their well-being. This may be particularly true if the stepparent already dislikes the children. If the newlyweds both have children, either party may show obvious partiality to their biological children, causing the other spouse to feel resentful.

Child support obligations can cause conflict. A stepparent may feel overwhelmed by the need to compensate for the biological parent's financial responsibility. Moreover, the stepparent is likely to become increasingly annoyed if the biological parent provides monetary assistance beyond what is absolutely necessary. This can be viewed by the stepparent as a subtraction of resources from the new family unit. Even will preparation and insurance policies can cause turmoil.

Newly married partners are likely to discover differences in parenting technique and discipline. One party might be lax, allowing children to eat dinner in front of the television. The other party may be fond of consistency and structure, with specific times of day dedicated to homework, bathing and sleep. One parent may shout at rambunctious children. The other may prefer time-outs or taking away toys and games. Addressing these matters prior to blending parenting styles will likely result in more compromise and less conflict later.

Children sometimes cling to the fantasy of their parents reuniting. This hope -- in addition to alignment with the other biological parent -- may motivate them to sabotage the new relationship. For instance, a child might disrupt intimacy between the new couple by insisting on sleeping in bed with them due to alleged nightmares or illness. Children may also share their new stepparent's personal information [traffic tickets, medical conditions or even just a glass of wine with dinner] with the other biological parent in an attempt to damage character.