It is clear from the book Deathwalker that Druss and Angel are related. However, what is not clear is how. We know that Druss' father was Bress and that his father was Barden. What we do not know is whether Barden is Angel's son or Grandson. We do know that Ekodas and Shia have a daughter who marries the young deaf child in Waylander 2. Their son becomes a mighty warlord, and their Grandson is mightier still. The mightier grandson is Ulric. The daughter is probably born soon after Waylander 2 in order for the age difference between the deaf child and the girl to not be that great. Angel's child from Miriel is probably born about two years after Waylander 2 so the pair of children are most likely of similar ages.
The daughter of Ekodas must have her son in less than 45 years from the time she is born. As the child becomes a mighty warlord, it is fair to assume that it is most likely one of the first born. This would mean he would have a direct next-in-line claim on the leadership of the Wolfshead tribe.
From this we can assume that Ulric, or Okai as he was called, could have been born anytime upto his father being 50. His father is still alive when Okai is 18 and runs the tribe. If Okai's father was 50 when Okai was born, he would be 68 and still incharge of the Tribe. As the Nadir are a very competitive race by nature, the leader of the Wolfshead tribe would be hard pressed to keep control of his tribe much past 70.
In all, there is most likely a maximum gap of 97 years between the ending of Waylander 2 and the birth of Okai/Ulric. This is maximum and I would guess around 25 - 35 years earlier would be the actual date. Therefore, there is a potential maximum gap of 146 years between the end of Waylander 2 and Legend.
If we compare the Angel - Druss line, we can see that there is a minimum of 81 years between Waylander 2 and Legend because the age of Bress is expressly mentioned. We also need to add to this the minimum time from the end of Waylander 2 that there could be for the birth of Angel's son. This would be 18 months minimum, but I would say closer to 2 years to allow for Miriel to get to terms with Senta's baby before having Angel's child. This puts a minimum of 83 years between W2 and Legend. However, the age of Barden also needs to be considered. He must have grow up enough to have a child, Bress, and I put this at about 20 years.
When Barden is killed, he was refered to as "the old wolf". There could be any number of different reasons why he was refered to in this way. He had also lived a life as a soldier, stationed at Dros Corteswain, and one as a Tyrant. Adding all the bits together, he must have lived a few years before he died, and the reference as "old" makes me believe he was fairly advanced in his life.
Adding Bardens age of 20 when he had Bress with the confirmed length of his life after Bress was born, 14, be can see he must be at least 34 when he died. Adding the 34 years to the 83 we already know about gives us a likely minimum gap of 117 years between W2 and Legend.
Comparing this with the timeline for the Ekodas - Ulric line, we can see a gap of 29 years missing form the Angel - Druss line. The difference here would allow us to take two different approaches on the situation. We could either fit in another generation between Angel and Barden or decrease the time between the Ekodas - Ulric and age Barden a bit more.
Fitting in another generation between Angel and Barden causes problems because it keeps the generation ages at their maximum on Ekodas' side and also keeps them at a minimum on Angel's side. Basically everything is very delicately balanced!
Not having a generation between Angel and Barden (making them father and son) and then reducing the generation ages from their respective extremes, gives the timeline more stability. Giving Barden the age of 55 when he dies and making him Angel's son makes the total time between Waylander 2 and Legend 124 years (67 years between Barden's death and Legend, 2 years for Miriel to give birth and 55 years life). Applying this to the Ekodas line, we can see that there is 22 years that can be taken off the maximum age gap between Okai's birth and the end of Waylander 2. Reducing Ekodas' daughters age to 25 for when she gave birth, and reducing Okai's fathers age to 48, we now have a fairly happy medium.
We could continue to take a few years off Barden and add it to either Okai's father (reducing his age from 48) or Ekodas's daughters age when she gave birth, but that is what is called fine tuning! And that is for David to do, after all, they are his stories!
It must be noted that it will never be 100% clear as to whether Barden is Angel's son or not until David writes another Drenai book and addresses the issue. All I have done here is taken what has been written in the books and applied a little bit of maths to it!