These dates are taken from a genealogy of the House of Bëor reproduced in volume XI of The History of Middle-earth (The War of the Jewels), and are not therefore strictly canonical, but they do fit the dates of other events described in The Silmarillion.
2
The published Silmarillion only shows the sons and grandsons of Boromir, but according to the extended genealogy in volume XI of The History of Middle-earth, he also had two daughters and three granddaughters. Of these, Bregor's sister Andreth and his daughter Bregil were particularly significant in their own right, though they don't appear in any definitively canonical sources. Andreth played a role in the philosphical dialogue known as Athrabeth Finrod ah Andreth, while Bregil was the grandmother of the hapless Brandir of Brethil.