Is a persons DNA likely to be more similar to the DNA of his biological parents or to the DNA of one of his first cousins

It is more likely to be similar to his/her parents because the get half of their genetic code from their mom and half from their dad.

Thats a good question but tbh i think it would be closer to that of his bilogical parents because half of are dna comes from our father and the other half from our mother so i would say the bilogical parents not the first cousin