Worried I won't get grandchildren

I have two kids, both a boy and a girl. My daughter had to have a hysterectomy when she was 15 because of cancer. She's 17 now and will never be able to have children. My son is 22 and he would have to leave his apartment to even get a girlfriend to have kids with. I visit him weekly and his home is always dirty. He does some type of online free lance job so when I say he doesn't ever leave his house, he doesn't ever leave his house. I have went over there just to clean his house because it gets so bad. He does have mental health issues. He has CPTSD and BPD so he struggles a lot and doesn't have insurance so he can't go to therapy. I'm just sad because I really want grandchildren. My daughter can't have kids and she has decided she probably won't adopt and just travel instead of trying to find another way of having kids and my son most likely won't even being able to get a girlfriend so I won't be getting grandkids from him. I'm 46. If I can't be a grandparent then what's left in my life? I'm about to have 2 adult children and nothing left.