2 Answers

That is going to take some organization and cooperation!  Maybe some of this will help.....

First, everyone needs ample space, needs to have supplies and books handy.....as in being prepared!

Second, there needs to be some rules about when you can be interrupted to provide tutorial assistance.  An example might be that questions that can't be answered without help get passed over and the student does all the work he/she can do without help.  That way, the questions are going to come all at the same time for one subject, and you can work uninterrupted until it's time to help with ALL the "hard ones". 

Is it possible that your siblings are able to help each other?  One may be really good at spelling and the other really good at math.  The more they help each other, the better for you.  It is also good for them; if they can explain concepts and others can understand them, they obviously know what they are doing.

Third, YOUR assignments come first for you.  If they have to wait while you finish something, then they wait.  They can fold some laundry, feed the dog or ??? while you finish.  Everyone has to be respectful of the work the other person is doing.

Fourth: Does it really take 3 hours for them to do their homework because there is so much of it or they honestly have problems doing it, or are they goofing around and dragging their feet.  It should be about 20-30 minutes of homework for each class in which homework is required.  They might be wasting alot of time waiting for you to carry them.

Fifth: You DO NOT do their work for them.  Guide them with the process, give them suggestions for completing their work, but they are responsible for coming up with the answers, not you. For math, you can demonstrate how to solve a problem, guide/talk him/her through doing one with you, then have them execute/talk through one on his/her own.  For answering essay questions, I always told my kids (and I subbed alot and told the students this, too), that the key to answering an essay question completely was by making sure the ANSWER written left no further question of who, what, when, where, why, or how.  Not every question is going to have all of those elements, but you can check your own answer by asking those questions and seeing if you have included it in your answer. 

This answer is way too long, but I really enjoy trying to help and solve problems.  Kudos to you for tackling 16 college units and being available to help your siblings at the same time!

You're a wonderful brother.  I'd just train them to do their homework.  If not, next year you'll be doing finite math and permutation for them.