Is it my responsibility?

I am the boyfriend/father figure to two undereducated children. Their mother was forced to become the primary provider (working 60-80 hours a week and leaving the kids education responsibilities in the hands of the "dad") for the family with an abusive cheating "father". The kids are 8 and 13 and are quite far behind and it seems like now I am the only person who cares about the kids education besides their mom. She is still working and I have time with kids. Should I educate them even if they argue and whine or is it not my responsibility? Should I let two children fall behind and become statistics on the system or should I take up the charge and teach them the ways of the world?I have been trying to do so so far the last 4 years and have had some progress but the children whine and struggle. They have shown progress but I am afraid of them disliking me for making them do things 80% of them family doesn't (such as math and grammar).(Name is an inside joke, sorry. lol) via /r/Parenting https://ift.tt/2VTdogb