Each person is different. You two cousins are different and might have different tastes in men. What work for the 21 year old might be off putting for the 50 year old.
By the way, since there are different men too, the idea that the 45 year old is being "emasculated" is absurd. After all, your 50 year old cousin is not doing things for him because she thinks he is unnable to do things on his own. Turn the concept around, isn't the idea that women can't do things on their own "efeminating"? After all, you 21 year old cousin can plan dates or put gas on her car, right? And what if the boyfriend is doing things in a way that doesn't quite work or even it is inconvinient? The way adults work is by asking for help when needed and handling things on their own. Sure, you can work together, reach arrangements and so on, but being independent and only asking for help when you really needed it is also OK.
How frail is someone self steem is they need to be with someone because they are needed instead of because that person simply enjoys the company and choses to be with the other?
Is not about being stuborn, it is about being happy with your life. The older you got, the more you know what you like and how you like things. You also know what you don't like and dislike. And usually you like things done a certain way. At that point is usually better to do it yourself or, yes, pay somepne to do it (the way you want) insteadoof asking, finding out that they have done it in a way that doesn't work for you and having a pointless discusion about that where you are called ungrateful for "not appreciating" what they have done for you. That happens to men too. At certain age, if they live alone, they like things certain way at their home, they like to cook their own food because they like it certain way, etc.
You might want to consider that each of your cousins have the relationship they want and that neither of them owe you to act differently to suit your idea of how women should act around men. And since the 50 year old has been in a relationship over two years, chances are that it is working for her boyfriend too. Besides, not everyone want to marry. Doing chores doesn't make a man. Maybe your cousin prefer that his boyfriend spend his free time doing something fun with her and not maintenance. Could be actual dates, sex or whatever thing they both enjoy. Why make him work longer hours when there is no need? Free time is scarce, I much rather go to dinner (or bed) than look how someone cleans my car. Just saying. XD