My DSis is in her late 30s and shares a very nice house with her DP, who has two DCs under 10 from his previous marriage. They come to stay with them every other weekend, and everyone has a happy time together.
DSis and her DP have a nice comfortable life and want for nothing, both work and earn very good salaries, have lots of weekends away, parties, etc. When they got together about 3 years ago, DSis said that she will want kids of her own one day. Her DP's response to this was, well of course kids are great, that's fine with me.
Trouble is he has now renaged on this and decided he definitely doesn't want any more childen.
She is devastated.
She first raised this topic with him nearly a year ago, when he first expressed doubts about having more DC's, and she gave him a year to think about what his final decision was. He has now told her that he's definite on this.
They are going for couples counselling.
I want to say to her "get out now while you've still got time for yourself", as I believe there's no prospect of him changing his mind. He's wasting her time, and knows he is. Thing is, if she's having any thoughts about giving up on the idea of her own DCs, I don't want to be too bombastic about it and make her shut down from listening to the possibility of any outcome other than an enormous compromise. She's terrified of the idea of losing him and their nice but empty life, and having to go through the trauma of selling up.
She wants to discuss this with me tomorrow when her she's back from a work trip. How do I help her? I'm so scared of her staying and funding herself in a situation in 5 years time when it'll be too late. 
Sorry, that's really long, but I'm so worried about her.