Put in what you know – you can always change it, and every change can be undone. Family trees grow from best guesses that get firmer over time! For a parent you're not sure of, you can add them as possible or probable rather than certain. For a date, put just the year if that's all you know. And if someone else knows better, they can put it right, and every change is recorded in Recent Activity.
Still stuck? Talk to a real person: send us a message, or email support@mywholefamilytree.com