Stepfamily Reality 27 - Legal Rights
Typically, re/marriage does not endow stepparents with the legal parental rights or responsibilities of bioparents. For example: unless authorized by a legal document called "In Loco Parentis" signed by both bioparents, typical (non-adoptive) stepparents can't legally demand to see their stepkids' school or medical records, and usually don't qualify as a legal guar-dian in hospitalizing a minor stepchild.
If the most loving stepparent dies without a will, their assets will usually not go to their stepchildren. Specific rights and laws vary by state, so ask a local family-law professional to tell you what pertains in your county - ideally before re/marriage!