2 Miis getting married
Marriage is a feature in Tomodachi Collection and Tomodachi Life, in which two Miis of opposite gender marry one another, becoming husband and wife.
The feature's benefits vary between Collection and Life. In Collection, two Miis that marry will not receive any form of reward other than the game acknowledging them as husband and wife. Life on the other hand provides many more bonuses to a married couple, rewarding them a house in Mii Homes, which they will live in along with their apartments. A married couple can have a baby with the players permission. Child Miis can also marry through use of Age-o-matic, which will instantly make them 18 years old.
Marriage is not guaranteed to be forever and divorce is possible, mostly if a fight between the two occurs and the Mii(s) is/are unable to resolve the problem between the two.
How Miis can marry
On Tomodachi Life your Miis or Islanders, what ever you would like to call them, can marry. But before they can marry two Miis have to be dating. One of the Miis will propose to the other Mii. It could take a couple of hours to a couple of days for one of them to propose, depending on their relationship. It took two of my Miis litterally 2 hours of being a couple for one of them to propose. But the rest of my Miis that are married took a couple of weeks. When one of them is ready to propose they will have the heart on their apartment, so be on the look out. They will say the saying you gave them for when they are worried if you made them one. Tap on the heart and they would say, I want to propose to _________. You can say yes or no to the proposal. Even kids can propose but I'll get to that soon. They will ask you if they should get changed, where they should propose, and if you can help them by telling them when the other Mii is thinking about them. When they are at wherever you told your Mii they should propose, you need to tap on the bubble when the Mii is being thought of. It will take four times until he'll/she'll propose. Once they propose the other Mii will either say yes or no. I never had a Mii say no before. Then they have the wedding. As I said I would tell you that kids can propose, they can. If they propose and the other one says yes then they will ask you to use Age-O-Matic to make them adults. I hope this answers your question about how Miis on TomoDachiLife can marry. :)
