yes isha's parents were all grown up and adults but they were too old to care for themselves and they needed their daughter. i believe we were shown a flashback sometime ago of isha saying "mai apne bete ko liye bina kahi nahi jaungi" followed by AS kicking her out. isha didn't leave to advance her career she left because she had to take care of her parents, she could not have let them just die, right? she left without ishaan because she was forced to by AS.
If not love triangle of bhabi devar .... " there is war of control deak bhabi " going 
72