As I understand it, adoption is for the benefit of the child and not for the purpose of finding a ruling royal. Of course in some cases adoption is necessary as royal families have more than one consort and so on. For example the current royal family of England. Whether a child should join the line of succession has to do with their merit. Are they a royal themself already? Is their spot in succession a regnant position or merely a prince or princess in title? The fact is when joined into a royal family all are welcome though not all are equal in stature. Adoption is for the benefit of the child and their life. In this day and age countless families are single parent families and many are multi-parent families. So in essence the answer is YES and NO. It depends on the child, the family and the country. Often in America, people do not adopt others children so that they will still receive child support from the biological parent. Often financial issues out weigh the emotional connections of adoption. The other key issues are blood relationship and percentage relationship to Queen Victoria. This is important for the purpose of pairing so that the royals lines continue in existence.