You asked us about AGE and this MATCHMAKER answered...

I recently turned 51 and my priorities in life have shifted. After a lifetime of bachelorhood and career-oriented pursuits, I want to get married and have children. I know this is only possible with a woman much younger than me. Am I being selfish or unrealistic? 

Amal and George Clooney

I'm happy to hear about your epiphany. Mazal Tov! Better late than never.  As a matchmaker, this is a scenario I see almost daily. To answer your question: you are not being selfish nor unrealistic- and nobody should tell you or make you feel otherwise. Each and every person needs to work on themselves and become at peace with who they really are before they can incorporate a second and third person into their lives. Your process took the time it required and you recognized that- it's noble of you. Now, it's time to find a lucky woman to bask in your many years of experience. From my experience as a matchmaker, you should be warned that it is not every woman who will fall under the spell of a silver fox like yourself. It will take a woman who herself engaged in a personal process and reached maturity and self-actualization quicker than the average. (Think Amal Alamuddin and George Clooney!)

Furthermore and not to sound cliche, age is just a number. Your goal is to set out to meet someone who recognizes that and is on your level in every single way permitting a deep connection. There's a Jewish quote that wishes you to live a long and happy life until 120 years old, as though you were 20 years old. I would like to conclude with this blessing to you and your future beloved. May you both always have the energy and laughter of 20 year olds no matter how old you are.

PS. Here's some scientific reading and not-so-scientific reading on the age question to help you decide how big your age gap should be.