The Take Care Clause and the Executive Clause. The President is the executive. If the President wants to have my cousin Dave conduct an investigation for him, that is his right. Just because past presidents have done things a certain way doesn’t mean that all future presidents must do it the same way. Do we at least agree on that?
What crime could the Biden’s have committed? A violation of the Foreign Corrupt Practices Act: Foreign Corrupt Practices Act - Wikipedia
You have Hunter Biden with no experience, no ties to Ukraine, no education, or any knowledge at all about oil and gas getting a lucrative position. This just so happened after Joe Biden demanded that a prosecutor be fired or else he would withhold $1 Billion in aid. Does that mean that one or both is automatically guilty? Of course not. But it is enough for an investigation. Or should they be immune from investigation because they are of the opposite political party of the current president?
I can guarantee you that if that was Donald Trump, Jr. that got that position, this board would demand Trump’s impeachment for that.