^^^ Usually the ships relate to a pair of ships' historical relations (whether they fought together or against each other), sometimes it's just because they're related ships (usually of the same class) but sometimes they just pop up from the fandom, something in the game or the anime (as was the case for the BelPrise ship).
For this particular ship, it relates partly to the fact that Massachusetts and Jean Bart fought each other during the battle of Casablanca during Operation Torch, the invasion of North Africa from the west.
The popular Prince of Wales x Prinz Eugen ship resulted from a similar reason, that both ships took part in the Battle of the Denmark Strait