on the immigration site ,hope it can helpMy mother do not remember date of birth of her sister and brother and we cannot contact them, can I just do guess work?
What do I put for the date of birth (or death) of my family member if I don’t know it?
If you don’t know the complete date, or if it’s in the 1800s, enter 1900 in the space for the unknown year, and 01 for the month or day. This will let you validate the form.
You should also attach a letter of explanation that says why you don’t have the information needed to fill in the complete date.