How can I find information about someones whereabouts?

My Ex-husband is supposedly dead, And I need to find information about him to get SSI for our daughter.How can I find information about someones whereabouts?The Social Security Death Index below may have him. It was last updated 31 Dec 2005. If not, but you have his SSN, the Social Security Administration may be able to help you.How can I find information about someones whereabouts?Follow Ted and good luck, though if you need help locating him, well look me up and I can certainly find him for you. $for a fee$