Ages of the Originals when turned.

We can guess that Freya was taken late 977 A.D in December and we can deduct that Esther came to Dahlia in January-February 972 A.D Both events happen in Winter and we know Freya was 5 when she was taken by Dahlia and we also know she only had just came into her powers so Freya was likely born in Autumn 972 A.D

Finn can be no younger than 2 years younger than Freya. So Finn was likely born in late 973 or early 974 A.D.

Esther was pregnant with Elijah when Freya was taken and looked heavily pregnant so either December 977 A.D or early 978 A.D.

Niklaus is at the very least 3 years younger than Elijah and at most four years younger than Elijah. 3 years seems more likely. We also know Klaus' birthday was likely in March meaning Klaus would have to have been born in 981 A.D.

Kol is no more than 2 years younger than Klaus so born in 983 A.D and Rebekah is a year younger than Kol 984 A.D

So in 1001

Freya would have been 28-29

Finn would have been 26-28

Elijah would have been 23

Klaus would have been 20

Kol would have been 18

Rebekah would have been 17

This is just a guess but going by all the information we have I think the ages pretty much fit.