From what I've observed Melania is the type who goes along with whatever her husband wants rather than make a scene. She takes a seemingly weaker position in the public perception of the family hierarchy, but no doubt Trump would do damn near anything she asked him to do - most likely she doesn't need anyone elses attention, approval, or notice because her world is likely centered around her home life - her son, her husband, and the rest of it doesn't matter. It's very likely that she's running the house like a queen; Trump can run around all day 'ruling the world' but I'd bet money his crown is left at the front door - though not as an 'alpha' power play, rather by choice out of respect for his wife. They seem to communicate through subtle 'gestures' - a wave of the hands, a tightening of the lips, a look, a light touch - its hard to describe, but I see the 'signs' because it's of a similar vein to the 'language' my husband and I "speak" in public. That's not to say appearances are nothing though, the straight armed stance both Trump's are taking speaks very loudly to 'formality' and doing things the 'right' way - which fits with Trump's oddities like always wearing a suit and the like. I also note that they stand in equal - their bodies squared as a united front to the world so to speak.
vs Mrs. Obama who I'm guessing always feels like she's got something to prove; she wants it out there that she's a strong woman, she seems worried feminists and idiots will think she's weak which is typical of someone who wants to be in the spot light (you'll notice Mrs. Trump has no desire to be in the public eye.) Mrs. Obama likely sees their marriage as a 'partnership' more than what you might call a traditional "male dominated" marriage (which in itself is misleading.) She's likely more independent, headstrong, and "feisty" than Melania is. It's likely uncomfortable for her to be seen as subservient to anyone, including Mr. Obama and he seems to respect that despite his personal demands for the same thing.
Conversely, Mrs. Bush is not only 'clinging' to her husband, but you'll note she's shifted the angle of her body so that she almost appears to be standing 'behind' her husband. Now, I wouldn't say she's less confident exactly, but I'd certainly say she was 'more traditional' in her views on marriage. She seems to want everyone to know that she's not the person they need to talk to. (Again, its not a bad style per say, merely a reflection of different opinions and upbringings.)
You'll note too that Mr. Obama shifts his shoulders similarly behind Mrs. Obama. I'd say she wears the pants, though I don't mean it as any kind of disrespect, its actually not as uncommon as you might think for the wife to rule the roost in private - most happily married men are more than happy to play sheep to their wives, and I'd actually say more common with alpha men who rule outside the home, doing that shit all day is draining, giving that power to the wife is an intimate luxury that's usually cherished. No doubt if I'd allow my husband 'submit' to me in such a way he would, but I demand that he challenge me at all times - I am not a very 'user friendly' wife