Some countries issue instant citizenship at the time of marriage. St. Kitts / Nevis still does that I believe. What other countries do this, and does it apply to both male and females marrying into a family of the country offering citizenship?

Some countries allow adoption even if the adoption parents are half the age of the person being adopted. For example, if you wanted to be from XYZ country and could find a family from that country willing to adopt you, you could grab a passport and residency from that country. I know this is true and have heard of it being done, but what countries still allow this?

Thank you.