Looking for Jeffrey Jacobs of Southern California

My hubby does not know his biological father, Jeffrey Jacobs. Hubby was born in April 1978, father not listed on birth certificate, born in Los Angeles. I want to find any siblings hubby may have from his father, rumored that he has sisters who are twins. I wish this wasn't so vague, but hubby was conceived as a result of an affair. Asking for information may hurt his mother, and I don't want to do that. If you have any info, I can provide you with more details privately. Thanks!