I find that most of our family 'secret' recipes are the result of trying several recipes for a given dish, picking the best one but incorporating lessons learned from the others. Its not uncommon for a page in our family book to consists of a photocopied page from a published cookbook + notes like "fully mix in the spices 1 at a time in this order:" where the recipe just says "mix in the spices".

Additional notes like "[cousin] likes this with more cinnamon, but [uncle] will always try to add more sugar" are helpful for holidays.