the david Milne family is in California by 1870 but all children born in Ontario. Can I find either marriages or births for the 1850-60 date. They give no town only Ontario as place of birth. Parents born Scotland.

Before venturing into Ontario research exhaust all leads that may give you a specific place of birth: death records, marriage records, newspaper notices, naturalization records, military records. Look at all the siblings, if you find a place of birth for one you have a place to start looking for the others.

Births & marriages were not required to be registered until 1869, so for earlier births & marriages you will have to look at church records (which means you'll need to know their religion AND the place where they were born). There are some marriage registrations available from the 1830's and can be found organized by county, so you will need to know the county of origin unless you have the time and resources to check them all. Another option is the 1861 census but again you should know where to look.