How can i find my half brother?

Question

i dont know his name or any other details other than h is in his 30s and was born in iowa ad my dad left before he was born

Answer 1

Without his mother's name or his name, you won't find him by yourself for free. You could hire a private detective. If your father is alive and speaking to you, you could ask him, but that possibility has probably occurred to you. You might ply the old man with drink to see if he will become incautious.

The internet is wonderful, but it isn't magic. His mom probably put "Unknown" for the father on his birth certificate, or, if she was seeing someone, his name.