Kim gelirse gelsin, toplantı saatinde başlayacak.

This is a very common Turkish pattern used to mean no matter who/what/where... or whoever/whatever/wherever....

In kim gelirse gelsin:

• gelirse = if he/she comes
• gelsin = a 3rd-person imperative/optative form, roughly let him/her come

But together they do not mean two separate actions. The whole expression works as one unit meaning:

• whoever comes
• no matter who comes

So the repetition is grammatical and idiomatic, not accidental.

By itself, kim usually means who.

But in this pattern, kim gelirse gelsin, it means whoever or no matter who.

So:

• Kim geldi? = Who came?
• Kim gelirse gelsin = Whoever comes / No matter who comes

The surrounding structure changes the meaning from a simple question word to a free-choice meaning.

-se / -sa is the conditional suffix, often meaning if.

So:

• gelir = comes
• gelirse = if he/she comes

In this sentence, the conditional is part of the concessive pattern X-se X-sin, which often gives the meaning even if X happens or regardless of X.

So kim gelirse gelsin is not just a plain conditional clause. It has the stronger sense of:

• regardless of who comes
• whoever comes

Yes, formally gelsin is the 3rd-person imperative/optative form of gelmek.

For example:

• Gelsin. = Let him/her come.

However, in kim gelirse gelsin, it is not functioning as a literal command. It is part of a fixed grammatical pattern.

So here, gelsin helps create the sense of:

• let whoever come
• no matter who comes

In other words, it contributes a feeling of indifference to the identity of the person.

başlayacak is the future tense: will start.

It sounds natural here because the speaker is talking about a specific future event: a particular meeting.

• toplantı saatinde başlayacak = the meeting will start on time / at the scheduled time

If you said başlar, that would sound more like:

• a general rule
• a habitual statement
• something like the meeting starts on time

So başlayacak is the better choice for a specific upcoming meeting.

saatinde means something like at its scheduled time, on time, or at the appointed hour.

It can be broken down like this:

• saat = hour / time
• -i = 3rd-person possessive suffix, giving the sense of its time
• -nde = locative suffix, meaning in / at / on

So saatinde literally comes out as something like at its time.

In this sentence, the most natural English meaning is:

• on time
• at the scheduled time

Yes, Turkish word order is flexible.

The sentence:

• Kim gelirse gelsin, toplantı saatinde başlayacak.

is very natural and neutral.

But you could also say:

• Toplantı, kim gelirse gelsin, saatinde başlayacak.

This version puts more focus on the meeting.

Even though Turkish allows flexibility, the original version is probably the most straightforward for everyday use.

It takes a singular verb here:

• kim gelirse gelsin

That is normal in Turkish. Even though kim can refer to any person and may imply multiple possibilities, the verb is usually singular.

This is similar to how English sometimes uses singular forms with words like whoever.

So learners should not expect a plural verb here.

Not a very natural one.

A very literal breakdown would be something like:

• who comes-if, let him/her come

But that is not how English expresses the idea.

The best approach is to understand it as an idiomatic unit meaning:

• whoever comes
• no matter who comes
• regardless of who comes

So this is a good place to avoid translating word for word.

Yes, very often. This is one of the most useful things to learn from this sentence.

Examples:

• Ne derse desin = Whatever he/she says / No matter what he/she says
• Nereye giderse gitsin = Wherever he/she goes
• Ne yaparsa yapsın = Whatever he/she does
• Kim ararsa arasın = Whoever calls

So the pattern is:

• question word + verb with -se/-sa
• same verb again, often in the 3rd-person imperative/optative

This is a very productive structure in Turkish.

The first clause, kim gelirse gelsin, sets up a concession.

It means that the result in the main clause will happen regardless of that condition.

So the logic is:

• Even if different people come
• It does not matter who comes
• The meeting will still start on time

That is why the whole sentence feels firm and decisive: the meeting schedule will not change based on attendance.