Often when the metalsmith arrives, s/he will have a spouse. However, there is no way to know this until you assign one of them a bed.
So, i suggest that a lowercase 'o' be placed after the sex symbol to represent that that dwarf is married. Maybe even followed by the name of the dwarf they're married to. This way, by letting the player know that the dwarf is married, the player can easilly avoid putting them into high-risk situations; mining, military, milling, lava forging, etc.
Also, for the enhancement of the atmosphere, married dwarves should equip themselves with a ring, or buy eachother a ring in their favorite material type. It gives a money sink for the dwarven economy, and a slightly emotional feeling (more so if it was a legendary dwarf) when you see a dwarven corpse with a ring on it.
That also said, whenever a spouse dies, the lowercase 'o' should be replaced with the striked-o, the symbol the spun silk (ie: after the dwarf collects it) uses, to represent the dwarf had a spouse, but that the spouse died. This could be applied to immigrants, to give them more of a history. They would also keep their ring, instead of discarding it -- unless these dwarves arn't highly emotionally tied to eachother. Theoretically, the more dwarves that marry and die to a dwarf, the more striked-o's will appear next to that dwarfs name...
Which should also reduce the chances of that dwarf getting a new spouse.