What kind of sentence is it?

[Jupiter]

Hi teachers,

I need you to tell me what kind of the below sentence is.

After a year, his wife came to join him, and since then they've had a daughter, so they decided to stay.

Many thanks in advance

Jupiter

[Pamela]

Hi Jupiter,

You want to know whether this sentence is comlex or compound, don't you?

If I were to answer, I would say the sentence being a compound one.

P.S. I wouldn't place a comma after 'year', but maybe that was the author's intention to make a pause.

[Yankee]

I'd call it a "not-particularly-well-written compound sentence".