...some of the older paperwork is hard to locate.

An account on Ancestry.com can be helpful. Family Search also has some records. If you knows where your ancestors were born or died, you could try requesting those records from that municipality or through VitalChek. Make sure every site you use to track the records is legit. A friend of mine said her search got her into a scam, which happily she recognized as such and veered away without harm. You mention "birth family" which suggests you are adopted. There are some different rules for adoptees, but beyond knowing they exist, I know nothing else.

Make sure to tell the story of the way you are connected in such a way that you have proof for everything. Dad's birth certificate shows his middle name as his first name, so we had to document how he was now referred that way on all our US documents, including my birth certificate. We included things like an old census from when he was a kid, his draft documents, a passport, my marriage certificate to show the link between my maiden name and married name. His dad's death certificate that showed he was born in the USA, which was how my dad got US citizenship. I duplicated copies of all the needed documentation for each of our applications, so that they could each stand on their own if separated. Simply mailing in the package was an adventure, with UPS being better than FedEx by far. Generating your own UPS label and bringing it to the UPS store will save you about $70 on shipping, as opposed to them creating and packing it up. They still attached everything for me.

We probably could have skipped the immigration lawyer, and indeed we only used her to get the birth certificate, but it made the process easier and between all of us it was not excessive.

I am very happy our family departure from Canada was so recent. My friend has to go back 4 generations. She will be mailing in an encyclopedia of information.

Happy historic adventuring!

IP