No blood relations..they aren't even relatives now since Arjun isn't married to either of Ankita's aunts (Purvi & Ovi) .Ankita might sacrifice her love for her little sister. Arjun is seen roaming around Ankita a lot. To this day I bet he is very fertile (4 kids in 18 months by 2 different woman). He is lonely whereas Ankita needs a support in the form of an older Arjun. Arjun is as fertile as ever 😆
It could be like the plot of Lambhe (starring Sri Devi). Anil Kapoor's character falls in love with Sri's. Sri marries someone else and has a daughter (who looks just like her years later) Sri's daughter falls in love with Anil and in the end they end up together.
With the jeeju-saali relationship x2, I don't see why this would be far-fetch. If Ankita is as argumentative as Purvi was back in the days, Arjun can easily fall in love with her.