Date based automation not from contact

When a visitor comes to my site, I want them to fill in the capture form with all of their relevant birthday data for each important person in their lives.

I will then remind them of those birthdays a week or so before. I can’t work out the right trigger set up.

For purposes of this example, let’s pretend the visitor has 2 nieces and 2 nephews, all with the same birthday, but different years.

Sally, 26/08/19
Susan 26/08/2020
Billy 26/08/2021
Bob 26/08/2022

If they are the uncle for all four of these people, they should receive 4 different automations containing different gift recommendations.

The requires AC to capture clusters of information relevant to their nieces and nephews: date of birth, gender, first name, etc.

The only available triggers were Contact Field and Deal Field which didn’t seem relevant.

Is this possible?