How to help my husband 😭

My husband is an incredible person, truly. We've been together 4, married a year and half and have an 11 month old son. He is an amazing father to our son and step father to my older children. It breaks my heart to see him so incredibly upset about his family. See, my husband is 18 years older than me so naturally there is some weird family dymanics. His sisters are 51 and 54, he is 49. His parents are 74 and 75. I am 31, my parents are 56 and 57. My family adores and accepts my husband as is, sometimes I feel left out because they can tell old people jokes (just kidding) lol but integrating into his family has been very challenging. From the beginning, his oldest sister has just been rude. It was to the point where I just avoided her all together. She an example, she shared with me that my husband must have figured out to be happy he has to stop dating trophies. She said that was a compliment to me and not intended to be rude. But let's be honest it was rude. His family is very passive aggressive and very emotionally disconnected. I believe when we got married is when my husband started to realize what they were like. On our wedding day, no one called him, reached out to him or did anything of that sort. I wish I would have known at that time, I would have made sure my brother and Dad was with him. (We had a very low key wedding) after the wedding we heard reports from my family and friends about how rude his family was, so the resentment started to build. Shortly after that, he asked his mom and sister to host my baby shower. Really the baby shower should have been an experience for them, our son is my husband's first child! The baby shower was a nice gesture, and I am unsure how to put in writing about how I feel without sounding ungrateful so I will just say it proved that his family doesn't know me nor do they respect me. His sister spent a half hour telling my 11 year old daughter about my husband's ex wife and girlfriends. All my baby shower games somehow involved something about "if mom could drink, what would she have" and I don't drink. So fast forward to now, a year later. So much more stuff has happened. They are toxic. I don't know if anyone has watched "Welcome to Plathville" but where Olivia said I didn't cause your dysfunction, I just discovered it? That is me. So about 2 months ago, with all the frustrations of their behavior building up over time, I blew the fuck up and I told his family to pound sand. I am done with them disrespecting me all the time and if they want to see our son they can call their brother/son. (Which is funny because they live 10 minutes away and they've see him maybe 3x this year) Now that the holiday's are over, I think this has really hit heavy for my husband. We've been fighting more, which isn't like us, so at therapy today I brought it up. My therapist believes my husband is hurt and upset with his family. We are getting ready to send out our sons first birthday invitations and I am dreading it. Not because we are inviting them but because I will have to watch my husband be in pain. Tonight, I asked him if my speculation was right and he broke into tears. He doesn't know how to tell his family they've hurt him. I guess they've treated everyone he's been with poorly so it's just a pattern of behavior and I don't know how to help him address it.