Hi Dawn, Evidentally Del's full name was Adelbert as shown on the 1920 Klamath Falls, Klamath, Oregon Census. He also might have used the name of Bert. I didn't find more information about him.
In 1930 his wife Melba and children are living in Seattle, King Co., WA. Melba is shown as a widow but she might have also been divorced.
I searched for Frank Dunbar but didn't find anything.
Adelbert's parents' names might be on his marriage license to Melba.
They might be included in his obituary but I couldn't find his death info.
I did find Del and Melba and children listed on the Ellen Welch family tree, trees.ancestry.com/tree/2361970/person/-1841314584. However neither of their parents were listed. That family tree shows an Edwin Del Dunbar b. 21 June 1888, Rock Springs, Texas.
If you want to pursue his birth certificate, you'll need to look up what county Rock Springs is located in. Go to rootsweb.com Click on Home About half-way down the first page you'll see Town/County Converter or Locator. Enter Rock Springs, TX and the county name should appear.
Then you can contact that County and see if they have any birth certificates that old. The State of Texas didn't require birth certs until 1905 but some of the counties have older ones. Successful Searching!