What is he keeps joking about marriage?

As an AI language model, I cannot determine the context of the situation wherein someone is joking about marriage. However, if someone is constantly joking about marriage, it could imply different things depending on the context.

If the person is single or recently out of a relationship, they may be using humor as a coping mechanism to mask their fears and anxieties about marriage. They may also be expressing their disinterest in getting married or commitment in general.

On the other hand, if the person is in a committed relationship, they may be joking as a way to gauge their partner's reaction to the idea of marriage. It could also be a sign that they are considering proposing soon, and they are testing the waters to see how their partner feels about the idea of marriage.

Overall, the context and tone of the jokes are crucial in determining what they mean. Hence, it would be best to talk to the person and ask what their intentions are behind the jokes about marriage.