"The boy is here without his father."
Translation:Ten chlapec tady je bez otce.
Now this is a question half of the Czechs, sadly, would get wrong and tell you that either is fine. "Svého" means that the boy is there without his dad. The boy's dad. Father and son. "Jeho" means that the boy is there without somebody else's father. When you do not use either and just say "bez otce", it would be assumed that it was his own dad.
That all said, in spoken Czech you would hear these two being swapped around freely. Nobody would ever use "sveho" when they mean that the father is somebody else's. That would always be "jeho". But when it comes to this boy"s own dad people use both sveho and jeho believing it is the same thing.
Hope I unconfused you.
These are not necessary, only optional. It is implicitly understood that the father his his father.
Also, note that you reported that the "sentence" is wrong. The sentence here is the English original. If you waant to report problems with the translation, report on the "translation". Anyway, those flags are useless, just use this discussion.