"My sister had an old sweater."

Translation: Моя сестра мала старий светр.

[punk-hobbit]

so if i say "someone had something", should i gender "had" according to the someone who had it and not the something that was had? (sorry if the wording on this question is confusing)

[alg1993]

Yes, exactly

[Holger631394]

How about "У моєї сестри був старий светр" ?

[deniko]

This is a perfectly natural sentence in Ukrainian, and it is on the list of the accepted answers.