Hi Handyson,
I have so far identified the following registration details:
Births of the three cousins and a marriage for two of them.
The births all showed the same maiden name for the mother.
Found her birth registration.
Found her parents marriage in 1908, and birth registration for her
four siblings by that marriage.
Her parents, both apparently dead by 1966, were living in
Goaters Road Ascot in 1911, but no sign of any useful Andersons
in the area that I could see.
Used the information found to match against family trees published
on the Internet. Two came up related to a sibling of your cousins'
mother but neither contained her or any of the other three siblings,
and no reference to Anderson. the material found lacked solid source
citations, and appeared to have been partly deduced from a census.
Now stuck trying to do the same for your cousins' father's family,
It looks like he was born out of county, and there is more than
one occurence of the name, so need some feedback from you if you have
any. The marriage cert for your cousins' parents could be useful,
especially if the groom's father had an unusual first name. Witness
names might also turn out to be useful. Details of your parents, and
their relationship to the father, would narrow down the possibilities.