Ates Parents are questionable too I believe.
In episode 10, Ates said both of his parents have no relatives. And whenever he asked, they would change subject and this is quite fishy. Firstly having no relatives is very unusual unless both his parents were orphans, if they were orphans then there is quite a lot of backstory to unfold. And if his parents are hiding their relatives from their kids then the big question is WHY?
Moreover, seems like S1 storyline is being repeated. Hazar came back for revenge, may be there is Ates parents role in tormenting Hazar as a kid, hence he is using Eylul like Ates used Mercan to enter in S1. Then Hazar will fall in love with Eylul. And like Ates learnt Mercan is innocent. Hazar also knows Eylul is innocent plus had a really bad childhood so he will sympathize with her. Plot is not exactly same but parallels can be drawn from season 1.
I just hope by the end of S2. All plot holes are solved.