There is also a point in the instructions to be taken care of:
"Child Status Protection Act protects children from "aging out" in certain circumstances. If your DV entry is made before your unmarried child turns 21, and the child turns 21 before visa issuance, he/she may be treated as though he/she were under 21 for visa-processing purposes."
But it depends on individual to individual case. BTW you mention you are already 21 yrs. old, so I don't think so your father can enter your details in his application"