[mandysummer]

I have a picture of a relative I am trying to locate, to be honest he is probably dead now as it was taken in the 1940's. He had a wife and children so there must be some relatives still alive.

[Curlyben]

If they are a relative try tracking them through your own family and friends first.
A picture taken 70 years ago would NOT really be of any use now, as people change..

[Fr_Chuck]

You look not with a photo, but with their name, last known address. From there people can start searching.

But in general you start by calling all family and friends who knew them and start collecting all the data you an.

[JudyKayTee]

I have a picture of a relative I am trying to locate, to be honest he is probably dead now as it was taken in the 1940's. He had a wife and children so there must be some relatives still alive.

In the US? If so he can possibly be tracked by his name and age (or date of birth) and relatives can also be found.