Mother was 12 years old

This could be correct, or could just be an odd numbering because most of the dates this far back in history are "circa," not exact.

Just remove the dates.

Most sources from that time period are sagas without any indication of dates and when you find dates on profiles it is usually fabricated by people who insist on having dates.
When two profiles are merged with different estimates you might end up with such a result. Geni are also missing basic genealogical date qualifies like before, after and between to tell that.

You should also know that even if the estimates is somewhat correct related to an event we can put a date on you will find some breaks in the logic and suspect that there must be missing some generations.
The reason is that in the Nordic as in many other cultures a source citation translation to "he/she was the son/daughter of some famous person" does not necessary men a direct son - it just means a direct ancestor like a grandson or more. In some lines like the biblical there are logical breaks that is up tp 30 generations if I remember correctly.

Well, if the parentage is correct the dates will work out. If not, they are the wrong parents. Ragnar was born 750, Aslung 755 His parents 709 and 720 Her parents 720 and 725. Ragnar and Aslaug's children: 777, 780 and 786. I worked it out.

Sandy

According to the 13th-century Tale of Ragnar Lodbrok, Aslaug was the daughter of Sigurd and the shieldmaiden Brynhildr, but was hidden while traveling (from Hlymdal to Spangareid) by Brynhildr's foster father Heimer. At the deaths of Sigurd and Brynhildr, Heimer was concerned about Aslaug's security (she was then 3yrs old), so he made a harp large enough to hide the girl. He then traveled as a poor harp player carrying the harp containing the girl. - The Sagas of Ragnar Lodbrok, 2009, by Ben Waggoner “all saga dates are speculative)