(Spoilers Extended)How should Aegon V have handled Prince Duncan?

Prince Duncan marrying Jenny of Oldstones instead of his Baratheon betrothed was said to have encouraged his siblings to also ignore their betrothals and do whatever they wanted.

Was there anything Aegon could have done in the aftermath of Duncan's marriage that would have ensured that Jaehaerys, Shaera, and Daeron did as they were told?