Sorry, but if he wants things to change, he's going to have to start making changes himself. He needs to take a good hard look at his lifestyle and decide what is important to him, and what he has just accepted along the way.
Does he want to do the amount of travelling for work that he does? Does his employer expect it of him, the single man, but not of the husbands/fathers (and wives/mothers)? If it is an inevitable part of the job, should he consider changing jobs?
Why does he have no house? If he works long hours he has an income, where is it going? Is home ownership unaffordable, or has he prioritised spending on other things (e.g. holidays, tech, fast car)?
Lots of people get sucked into a lifestyle that's fun in their twenties, and then somehow they get stuck. He's realised that's where he is now, I think the best you can do is encourage him to have an actual life-plan rather than just drift with the opportunities. To sit down, work out where he wants to be in three or five years time, and to consider what he's going to have to put in place to achieve those goals. To position himself to be able to meet someone, to build a relationship, to get on with his life.