
One DNA test alone does not help you find your DNA relatives.
Why? Because AncestryDNA or 23andMe help you find your DNA relatives from their user base, your potential relatives are not necessarily purchased the same DNA test kit service as you. If you purchased AncestryDNA and your unmet genetic family bought 23andMe, you would never be matched, and vice versa.
The only way to maximize your chance to find your DNA relatives is to use multiple DNA tests or sites.