When Social Security was set up for traditional families, the retirement or death of the husband would cause great hardship. Therefore, the government program was designed to protect spouses and other dependents of workers who paid into the system. That may not make as much sense today, according to ProPublica in "How Senior Daddies -- Like Donald Trump -- Are Eligible for a Social Security Bonus."
One of these old protections is something that even very wealthy people, like President Trump, can take advantage of. People who receive Social Security benefits with minor children as dependents, can get extra benefits. In the President's case, that could amount to an extra benefit of about $15,000 a year, until his son Barron grows up.
It is not known if the President is getting this bonus or if he is even taking Social Security benefits at all. If he does take it, he joins the 1.1% of people on Social Security who also get this bonus.
Reference: ProPublica (March 2, 2018) "How Senior Daddies -- Like Donald Trump -- Are Eligible for a Social Security Bonus."