# Is there a convention for estimating a parents D-o-Birth based on a known D-o-Birth of a child?

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I have read the section on "unknown" items and "estimates".  I have a firm D-o-Birth for my great, great (larsen-2800).  Based on that date (1817) since I also had his father's name I noted the father's birthdate as "before 1817".  This shows up on the error report as father too young or not born yet.  So what is, or is there a convention for making this estimate?  Thanks.
WikiTree profile:
I use for the father 25 years earlier, the mother, 20 years earlier.  In the few cases I've found actual dates they have been within one year of this.  No explanation, it just works.
There are also 2 templates called {{DateGuess}} and {{DateGuess2}} to help in these cases.

Here's a link to the list of templates.

http://www.wikitree.com/wiki/Templates

+1 vote
I had the same issue when I would do the same thing but in my family tree software (Family Tree Maker). For that particular software, I think the parents' ages had to be a minimum of 13 years older than the first child. However, in my experience with the families I have dealt with (Canadian/Irish mostly), a trend emerged quickly with regard to how old people were at particular milestones. For example, most girls married between the ages of 16 and 21, and I don't think I have found a man yet who married before the age of 18. Typically, the first child was born about 2 years after the marriage, with subsequent children occurring every 2 years after that.

Generally, my estimates look like this:

If the known or estimated DOB for child = 1850

Then the estimated year of marriage for parents (less 2 years) = 1848

And estimated year of birth for mother (less 16 years) = 1832

And estimated year of birth for father (less 18 years) = 1830

I would say if your grandfather was born in 1817, then I would estimate his parent's marriage in 1815, his mother's birth about 1799, and his father's birth about 1797.

I hope this helps!!
by Christine Daniels G2G6 Pilot (125k points)
I do something similar to Christine.  I prefer to use "before" style estimates for birth (and after for death).  When I use the before style estimate, I use 16 for males and 14 for females.  But I rarely find evidence of folks marrying that young.  Typically the men are 25-30 or even 50+, and the women are 20-30.  But since the before is a minimum date counting backwards that's OK.  If I wanted to use "about" for some reason to try to maybe have a more accurate date, I would likely use 25 for men and 20 for women (with sort of a +/- 5yr interval in mind), but it's still just a guess that could be off by 20-30 years.  I rarely guess on marriage date, and on death date only if I have something to give a useful estimate.
by Living Anonymous G2G6 Mach 4 (47.5k points)

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