By not understanding some basic differences AND the fact that stepfamilies experience a normal developmental process which takes time, many remarried couples create unnecessary and painful problems in their stepfamilies. Biological Family Marriage created without serious loss and with great expectations. Shared history and traditions. Couple relationship predates parent-child relationship. Family roles and rules evolve.
Biological parents have legal rights regarding children.
Both biological parents live in household. Children live in one household. Children arrive one at a time, over time. The Stepfamily Family born of loss with death or divorce of parent. Two fully developed, and often diverse, sets of traditions.