Why can't our side and the enemy have the same role

I am editing fe7 and I have added Lloyd and Linus to our pre war preparations, but as soon as I see the enemy’s Lloyd and Linus, they will disappear. What’s going on?

You’re not giving very clear information. But I think what happened is that you used the same Unit ID Loyd and Linus.

In GBA FE, you can’t have multiple of the same unit if at least one is on the player side, I reckon. You would have to make a duplicate Loyd and Linus. One for the player, one for the enemy.