My Dynasty has just joined the group of those who have been "blessed" with multiple births without doing anything to cause it. And in my case, it is definitely not wanted. With Generation 5 just born, the house is now full. Gen 3's husband is old and probably won't live much longer, but the twins' mother will have to die before the immortal twin can marry and have a child, and she has just turned Young Adult herself. If she lives as long as Christopher Steel in Pam's game, my Gen 5 will be old and grey before he can reproduce. Fortunately he's male, so that won't be a Dynasty-breaker, but if the twins were female, I'd be feeling worried.
I'm wondering if consideration needs to be given to allowing a second child or older spouse to be moved out in the event of unexpected multiple births. As I said, it won't be a problem for me, but if it happened in a later generation or with female children, it definitely could be.