According to the cladogram which group of organisms is the closest relative to chordates

Cladogram which are closest relative to chordates also have the four characteristics.

The four basic characteristics of phylum Chordata. It has a dorsal nerve, a notochord, a post annul tail, and pharyngiall gill slit.

Jawless fish, cartilaginous fish, and bony fish have notochord when they were still young but it was replaced by a vertebral column as they mature.

Lancelets are included in the subphylum cephalochordata. Cephalochordates are gonochoristics. It means that the sexes are separate. Both sperm and eggs cells are released in the water where fertilization occurs.