Your boyfriend must be very, very special for you to stand by him and have 2 children with him in spite of 5 years of this. Taking care of the situation is long overdue for all of you and especially for your children.
From what you’ve told me, I don’t think your boyfriend is having an affair. My guess is that he is emotionally stuck. He has never resolved the death of his grandfather or his relationship with his bio-dad. Bereavement may have moved to depression, complicated by fear of being abandoned yet again. After losing his grandfather, your boyfriend seems to have turned to his own father to fill the role of adult guide. Unfortunately, his father is a terrible role model for what it is to be a responsible man and a good father. To have a relationship with him, your boyfriend has had to fall into the role of being an equally irresponsible “brother.” Meanwhile, you don’t have a real partner and your children are watching these men (their dad, your roommate, their bogus uncle) and learning that this is the way that men relate to their families.
Sadly, your boyfriend doesn’t see anything wrong with the situation. He is unlikely to seek help so it’s up to you to initiate change. Is there enough positive in your relationship to put in the time and effort required to make your family work? If so, it would be a really good idea for the two of you to get into counseling. An experienced therapist would help your boyfriend untangle his feelings about his own family of origin and figure out why he is sometimes suicidal. He might then be able to make better choices about how to be a husband to you and a father to your children. You would learn whether you have inadvertently had any part in creating the situation and what you can do to support change.
Will your boyfriend refuse to look at any of this? Then you have some hard choices to make. I hope you are not so financially trapped that you can’t afford to separate until he can turn his attention to you and the children. Whether or not separation is financially possible, I suggest you find a counselor for yourself and an Al-Anon meeting. A counselor will help you remember that what is going on isn’t normal and will support you in learning how to help your children. Although your boyfriend isn’t necessarily an alcoholic, his relationship to his family is much like one. At Al-Anon, you can learn how to detach from his issues and protect and support your children. The number to call to find out about the location of Al-anon meetings is 1 800 344 2666.
You have a complicated and diffficult time ahead. I hope you will do what you can to take charge of the situation. You and your children and your boyfriend all deserve so much better.
I wish you well.