Like in Fire Emblem: Awakening, you can develop character relationships and increase their support ranks. Once they reach rank S, the two of them will marry and in most cases, produce an offspring that will inherit the skills of the parents. Marrying off your characters is entirely optional. However, you'll miss out clearing the offspring's designated paralogue mission. These missions usually contain rare items and unique bosses that can be captured.
Benefits of Marriage
Married Avatar Events/Changes
The character your avatar married will stay with you in your Private Quarters. The dialogue for some visitors you invite to your quarters with your partner will be altered a bit as well.
There are *toned-down* interactions that you can do to your partner to increase your bond, like gently waking your partner up by caressing the touchscreen, blowing the steam off your partner's face after a bath, and get a unique shared bath scene with your partner.
Marriagable Characters
There are some special characters that can only be married to the avatar, depending if the avatar is male or female. Some examples would be Reina, Scarlet, and Shura. There are also some characters that can't be married like captured bosses, other players' avatars, and those who are restricted due to their part in the storyline.
The avatar can also marry the offsprings of other characters, (which further complicates the family tree) and the children can also marry each other but they won't produce any offspring at all. So far, only the avatar can be paired with the offspring characters.
Same-sex Marriage
There are only two characters in the game that can have same-sex marriage: female characters can pair up with Rhajat (Offspring, Hoshido) and male characters can pair up with Niles (Character, Nohr) No offsprings will be conceived in this setup so if a male avatar pairs up with Niles, Kana and Nina won't be born. Normal S-support events and benefits will still trigger as normal.