I do not think there is a connection. So far I have found 4 William Allans. They were born in 1816, 1844, 1846, and 1879 so it does not seem to be the same person. Also the Aitken name does not fit this date either. Have you tried this web site :- www,scotlandspeople.gov.uk It is the official web site of The Scottish Registry Office. You can search for, and download copies of birth, death and marriage certificates back to around 1500. If you have any questions, please let me know at firstname.lastname@example.org.