You say that you’ve recently met this woman. Imo you need to give the relationship more time before leaping in and telling her to get rid of him.
There are some good pieces of advice above.
Where indeed is his father?
Also I’m guessing that he is her little baby and she’s not yet prepared to ask him to leave, however if your relationship carries on in the way you hope, she may have the courage with you at her side to slowly get him to change his ways, at 29 years of age it’s not too late.
If you live close enough maybe you could arrange she eats with you and uses your fridge, thus emptying out all the food from his grasp, he’ll then have to start taking responsibility.
Also not washing or ironing his clothes etc.
If you do end up asking her to make a choice I think you’ll lose at this stage.
With anyone who has extra baggage any relationship is difficult, you need to find the compromise and work something out, or walk away.
Good luck.