Brothers at war

Our 2 sons became engaged within months of each other. One spoke vaguely about getting married in 2028 due to finances being tight, though his fiancé was keener on 2027.
The other brother got organised straight away and booked his wedding for Autumn 2027.
His brother had announced that things have now changed and he’s getting married 10 weeks before his brother. This announcement has caused world war 3 to break out. One brother feels hurt, that it’s been done deliberately to upstage him and his bride and is basically angry. He had disinvited his brother and future SiL to his engagement party. He wants his brother’s wedding to be moved. We are horrified and under stress to see the boys at war with one another. We feel torn. Old hurts have resurfaced and we have been accused of having a favourite. We recognised they feel hurt and that some of their moment had been taken from them, but equally feel it’s not the end of the world and that both boys should concentrate on their wedding and enjoy this time in their lives.
Can any one help advise how to navigate , jerk this situation. Our fear is this is just going to escalate, as each becomes more stubborn and digs in their heels .