I am trying to help my father locate his possible siblings and also try and figure out who his biological father could be. I've gotten pretty far with finding a lot of information on his birth mother (who used so far up to 5 different last names through out her life) and have found 4 half siblings of his.

I have tried many sites claiming to beable to locate vital records in an effort to search birth records by using the mother's name (my biological grandmother always seemed to put her correct name on the birth certificates) but have had no luck. Any one know of a way I can find birth records from 1940's-1960's for Kansas, (possibly Iowa, Missouri, Indiana, Texas) by going through the mothers name listed on the birth certificate?
Also I am trying to find any type of marriage documents for said time frames and states. The main state i'm trying to find information from is Kansas. this is where the brick wall is and I have no idea about marriage dates or divorice dates....