A number of players were a little bewildered when, having experienced all Heart Events for an Eligible Girl/Bachelor and having met all other ordinary requirements for marriage, the individual, at deepest red heart, would refuse the player's Proposal and Blue Feather.
There is an added requirement for marriage in Sunshine Islands that is related to Sun Stones. Where Characters in Sunshine Islands are concerned, there are two different types of Sun Stone Gifts. One is given after the player has given give 'Favourite' items as gifts. This little Event can occur anywhere on the Map when you speak to the individual after having given five Gifts that have been received 'with music'.
There is another Sun Stone, in many cases, that you can receive from a Character as well. This is the Sun Stone that is given as 'owner' of a house or business. In the case of any Eligible Girl/Bachelor, it is only those who have their own houses or businesses that will give this Sun Stone to you.
Why is this a requirement for marriage when only some Eligible Girls/Bachelors live by themselves? The reason is that, once you marry the individual, he/she will come to live with you in your Farmhouse. This Sun Stone Event, which occurs at two hearts, only can be triggered when you enter the home of the individual who owns it. Once you are married, the individual no longer will be at his/her old address. This must be the reason why the owner's Sun Stone Event must occur BEFORE you are allowed to marry the individual.
In the ordinary course of gameplay, most players never will be aware of this Sun Stone requirement for marriage. In my own first game, I collected as many Sun Stones as possible as early in the game as I could. I therefore had received all possible Sun Stones from every Eligible Girl and Bachelor long before I had experienced all Heart Events.
It is possible, however, that a player may raise heart levels and experience Heart Events without ever entering the home of the Eligible Girl/Bachelor to trigger the owner's Sun Stone Event. After all, it is easy to create a routine where you meet and greet every Character in the same location day after day. Often, it is most convenient to greet Characters at the Cafe or Diner in a single visit rather than entering every home on every Island. Where some one like Shea is concerned, you may meet and greet him when he is outside his tent rather than doing so when he is inside. Where Will is concerned, you may neglect to visit him on board his ship after he reaches two hearts to obtain the Sun Stone he gives as 'owner'.
Evidently, Heart Events pre-empt Sun Stone Events in these situations. Otherwise, players who enter a home in order to trigger a specific Heart Event automatically would experience the Sun Stone Event first... In any case, players need to be aware of the fact that you must obtain every possible Sun Stone from an Eligible Girl/Bachelor before you will be able to propose successfully to him/her.