Hi Viv
They might not be in a phone book 50 years later

,what kind of phone book did you look in that dint give an address

unfortunately we cant help you look for living people but you never know this post might get seen by someone who knows or knew the family

I don't think it would be a good idea to phone people up

So may i suggest that you put an add in a weekly paper in the area they lived.Then if they want they will contact you,or there are special websites like lost cousins,CuriousFox and a few others