Can i marry without a wali?

Assalamualaikum! I Got engaged in jan 2023 and our parents decided that we’ll wait for 2 years before marriage but because of our studies our parents want us to be settled first so they are going to stretch it more. We don’t want that i’m 24 he’s 25 we both are mature and independent. My question is if my father is okay with the guy but he just wants to delay it, will the nikah be valid if we do it without the acknowledgment of my father or do i need a wali? I have a younger brother who is 20 and if i ask him he will support me. Can he be my wali? We tried persuading our parents but they won’t budge from their decision. Thank you.