Rapat keluarga besar akan diadakan pada Juni di rumah paman saya.

In this sentence, keluarga besar usually means extended family: not just parents and children, but also uncles, aunts, cousins, grandparents, and so on.

Literally, besar means big, so word-for-word it looks like big family, but in real usage keluarga besar is a very common expression for extended family.

So rapat keluarga besar is best understood as a meeting of the extended family.

In Indonesian, adjectives usually come after the noun they describe.

So:

• rumah besar = big house
• keluarga besar = literally big family, commonly extended family

That is different from English, where adjectives usually come before the noun.

Akan diadakan means will be held or will take place.

• akan = marks the future, like will
• diadakan = be held / be organized

So:

• Rapat keluarga besar akan diadakan... = The extended family meeting will be held...

This is a very natural way to talk about planned events in Indonesian.

Because Indonesian often uses the passive when the focus is on the event itself, not on who is organizing it.

Compare:

• Rapat keluarga besar akan diadakan pada Juni... = The extended family meeting will be held in June...
• Keluarga kami akan mengadakan rapat keluarga besar pada Juni... = Our family will hold an extended family meeting in June...

The first version sounds natural when the important thing is the meeting.
The second version is used when you want to emphasize who is organizing it.

This is a very important distinction.

1. di- as a prefix is attached to a verb and often marks the passive.

   • diadakan = be held / be organized

2. di as a separate word is a preposition meaning in / at / on for location.

   • di rumah = at home / at the house

So:

• diadakan = one word, passive verb
• di rumah = two words, preposition + noun

This is one of the most common spelling points for learners.

Not always, but it is useful because it clearly marks the future.

With akan:

• Rapat keluarga besar akan diadakan pada Juni... = clearly will be held

Without akan:

• Rapat keluarga besar diadakan pada Juni...

This could still be understood as future if the context is clear, but Indonesian often leaves tense to context. So akan helps make the meaning explicit.

In other words, akan is not always required, but it is very normal and helpful here.

Pada Juni is a standard and natural way to say in June, especially in slightly more formal Indonesian.

• pada Juni = in June

You may also hear:

• di bulan Juni
• sometimes di Juni in casual speech

But pada Juni is a good, correct choice in a sentence like this.

A simple way to think of it:

• di is most strongly associated with place
• pada is often used for times and more formal time expressions

Because Indonesian possession usually works like this:

thing possessed + owner

So:

• rumah paman saya = my uncle’s house
• literally: house uncle my

First you say the thing, rumah, then who it belongs to, paman saya.

This is very common in Indonesian:

• buku saya = my book
• mobil teman saya = my friend’s car
• rumah paman saya = my uncle’s house

Because possessors come after the noun in Indonesian.

So:

• paman saya = my uncle
• ibu saya = my mother
• nama saya = my name

English puts my before the noun, but Indonesian puts saya after it.

You can think of paman saya as literally uncle of me, though in natural English we say my uncle.

Because Indonesian does not normally use articles the way English does.

So a noun like rapat can mean:

• a meeting
• the meeting

The exact meaning depends on context.

That means:

• Rapat keluarga besar akan diadakan...

can naturally be translated as either:

• An extended family meeting will be held...
• The extended family meeting will be held...

depending on the situation.

This is very normal in Indonesian, so learners have to get used to using context instead of articles.

Yes, Indonesian word order is somewhat flexible, especially with time and place phrases.

For example, these are both natural:

• Rapat keluarga besar akan diadakan pada Juni di rumah paman saya.
• Pada Juni, rapat keluarga besar akan diadakan di rumah paman saya.

Both mean the same thing. Moving pada Juni to the front gives it a little more emphasis, like As for June... or In June...

The basic sentence pattern is still clear:

subject + future marker + passive verb + time + place

So the original sentence is natural, but other orders can also work.