We are never told about CW's background, how his father earned his living, how or when his parents died.

I speculated at one point that CW's father might have been a sea captain also, or somehow connected to the sea trade by living in a coastal town. Which might have prompted CW to enter the navy.

So another possibility is that Croft served on board ship with CW's father, which might also explain how Sophie had heard of Croft long before meeting him, and he of her.

But I think Rae has it perfectly right, that CW had served under Croft early in his career. This would also explain how Anne immediately recognized the name Croft, because CW would have spoken of him more than just in passing as the husband of his sister, if he admired Croft and had been instrumental in making the match by writing about Croft in his letters home to Sophie and speaking of his beautiful sister to Captain Croft!

Which led me to think, was Sophie on board ship married to Croft at the same time as CW? Because CW must have served under Croft at the start of his career (aged 18-23 perhaps) having just been made a Commander (Captain) when Anne first met him.

Going back to ch. 4 where JA first introduces CW, I have reread the lines where CW had been made a Commander "in consequence of the action off St. Domingo." Definately the island of Hispaniola in the West Indies (though I am weak on the rest of the reference, which would have been obvious to readers in JA's times -- my assumption is that this refers to Sainte-Domingue or present day Haiti, the most valuable colony on earth at the time due to its sugar and slave trade and belonging to France until 1804.)

Since Sophie says she has never visited the West Indies, this must date her marriage AFTER the action off St. Domingo if Wentworth was serving under Croft's command. The Crofts are away at sea in 1806 when CW and Anne first meet, probably as newlyweds.