I know exactly how you feel. My family is also very close which my husband really likes. My FIL passed away almost 11 yrs ago. He was an alcoholic....but he was always there for his kids and provided for them very well. They were bought anything and everything....but the one thing money couldn't buy...was the love and closeness that they missed. But when my FIL got sick and was in the hospital from May until July, I went to the hospital almost everyday (but that was how I was raised and I didn't want to have any regrets because my FIL and I had our differences also)....but my husband only went a few times. I tried to get him to go with me but he had no desire to go....but I think if he knew then how he would feel now....that he would have went and been the better person. There is nothing he can do about it now!
To this day my husband still goes through bouts of depression and missing his dad. And I'm sure regrets about their relationship. I love my MIL....but she didn't help the matter by staying married to him and voicing her feelings to the boys. He messed around on her alot....but he provided well so she stayed
I remember when my stepson was about 5 yrs old and how hateful he talked to my FIL because that is how he heard my MIL talk to him....it was really sad.
Anyway, I just wanted to say that I am sorry for what you are going through right now. If at all possible....I hope your husband puts his feelings aside, for now, so that he doesn't have any regrets later on. Plus, he needs to set an example for his kids and show them that sometimes we have to set our differences aside in order to be a better person in the end!
Tina