Hemichordates and echinoderms are considered sister groups since they share similar relationship with each other. However, genetic evidences show that they needed to be separated for certain reasons as well. These two phyla are the nearest relatives of chordates; organisms that has a notochord.
Their significant resemblance is their larval stage. Echinoderm larva is a bilateral in shape which is similar to the larval stage of hemichordates. They also have similarities in the arrangement of their coelomic cavities and early embryogenesis.
Differences occur as echinoderms are in adult stage. From a bilateral larva, they transform into radial shape organisms. They also possess tube feet and their bodies are covered with skeleton made up of calcite. Hemichordates have gill slits and a rudimentary notochord; dorsal and ventral nerve chords.