Re: Birthday Problem of aging sync
Hi @death-flower246 - If you want them to both age up at the same party, just have each of them blow out candles on a cake. You can choose more than one sim as the birthday sim when you plan the party.
I think the easiest way to do it the way you want to is to bake 2 cakes before the party. Add candles to both of them immediately, so no one will eat the cake. You can put them in the refrigerator with the candles on top and no one will bother the cakes until you tell them.
Then, throw the birthday party - select both sims as the birthday sim. When you're ready, have each blow out the candles on one of the cakes and they will both age up.
(Just so you know, you don't have to throw a birthday party at all, or even have the birthday sims selected. If a sim blows out the candles on a cake, they will age up, whether there was a party for them or not.)