Of course the one and only obvious exception here, which obviously goes without saying and is nothing more than a one-off situation, is that you wouldn’t mix an under 18 minor with an 18+ plus adult unless they were already together before either one turned 18, and while together, one turned 18 before the other or until they both reached 18, if they weren’t already together, because most states consider that one-off situation not legal to begin with.

Other than that lone one-off situation, there is no reason for anyone or anything to stand in the way of love if two people truly love each other. Above all, no one can live the two people’s lives for them except themselves, and if there ends up being a major age difference but the two people truly love each other, then their happiness should come first, and everyone else should be able understand the importance of this fact because everyone else would want (and deserve) the same consideration, if it was them, as the two people want (and deserve).