Learn Hardcore Turkish: Kız kardeşim utandı, ben ise gülmeye devam ettim. - My sister felt embarrassed, whereas I kept laughing.

ise marks a contrastive topic: “as for … / whereas …”. It contrasts the second clause with the first: “My sister got embarrassed; as for me, I kept laughing.”

ama is a coordinating conjunction meaning “but” and links clauses: “Kız kardeşim utandı, ama ben gülmeye devam ettim.”
de/da means “also/too,” not contrast. “Ben de gülmeye devam ettim” = “I also kept laughing,” which would imply your reaction was the same, not opposite.

Can I write bense instead of ben ise?

Yes. bense is the fused/clitic form and is very common, especially in writing. All of these are natural:

“Kız kardeşim utandı; ben ise gülmeye devam ettim.”
“Kız kardeşim utandı; bense gülmeye devam ettim.”

Why is there a comma, and could I use a semicolon?

You have two independent clauses. A comma is common in everyday writing; a semicolon is also good (and slightly more formal/clear):
“Kız kardeşim utandı; ben ise gülmeye devam ettim.”

Why is the pronoun ben expressed? Isn’t the subject on the verb already?

Turkish usually drops subject pronouns, but they are used for emphasis/contrast. ise needs a topic to attach to, so ben (or the fused bense) is expressed to mark “as for me.” Without contrast, you could just say “Gülmeye devam ettim.”

What exactly is utandı morphologically and aspectually?

Root: utan- “to be/feel embarrassed/ashamed”
Past tense suffix: -dı (harmonized as -dı here)
3rd singular: zero ending
So utandı = “(she/he) got embarrassed” (a completed past event). Note: utanmak often takes the ablative for the cause: “bir şeyden utanmak.”

How is gülmeye devam ettim put together?

gül- (to laugh)
-me (verbal noun/masdar: “laughing”)
buffer -y-
dative -e → gülmeye (“to laughing”)
devam et- (“to continue”) + past -ti
- 1sg -m → ettim
  Altogether: “I continued (to) laughing” → “I kept laughing.”

Why is it gülmeye (dative) and not gülmeyi (accusative)?

Because devam etmek selects the dative case for the action you continue. Compare:

“X yapmaya devam etmek” = to keep doing X (dative)
“X yapmayı bırakmak” = to stop doing X (accusative)
“X yapmaktan vazgeçmek” = to give up doing X (ablative)

Could I say gülmeyi sürdürdüm instead?

Grammatically possible but much less idiomatic. sürdürmek is transitive and is most natural with nouns (“Görüşmeleri sürdürdük” = “We continued the talks”). For activities from verbs, Turks overwhelmingly use -meye devam etmek: “Gülmeye devam ettim.”

Where can ise go in the sentence? Can it appear after the verb like ettim ise?

ise typically follows the topic/focus element: “Ben ise …” or “Kız kardeşim ise …”. You can mirror the contrast:

“Kız kardeşim ise utandı, ben gülmeye devam ettim.” It does not go after the verb in this meaning. Post-verbal -se/-sa forms like ettimse mean “if I did,” which is a different (conditional) function.

What does kız kardeşim tell me that kardeşim alone wouldn’t?

kardeşim = “my sibling” (gender-ambiguous, often implies a younger sibling in everyday use).
kız kardeşim explicitly marks female gender: “my sister.”
If you want to specify age: ablam = my older sister; küçük kız kardeşim = my younger sister.

Could I replace ise with ama and keep the same idea?

Yes, but the nuance shifts slightly:

“Kız kardeşim utandı, ama ben gülmeye devam ettim.” = plain “but.”
“Kız kardeşim utandı, ben ise gülmeye devam ettim.” = topical contrast, “as for me/whereas I…” Both are correct; ise feels a bit more contrastive and structured.

What are the differences among utandı, utanıyordu, and utanmış?

utandı: simple/definite past, completed event (“she got embarrassed”).
utanıyordu: past progressive (“she was getting/feeling embarrassed”).
utanmış: evidential/inferential past (“apparently/she seems to have gotten embarrassed,” speaker didn’t directly witness or is presenting it as inferred/hearsay).

Why does ettim have a double “t”?

From et- + past -di. After a voiceless consonant (t), the past marker surfaces as -ti, giving et-ti; with 1sg -m → ettim. The double “t” is from the root-final t plus the t of -ti.

If I want to say “I kept smiling” rather than laughing, what changes?

Use gülümsemek (“to smile”):
“Gülümsemeye devam ettim.”
The structure stays the same: verb stem + -me + (buffer) -y- + dative -e + devam ettim.

Is there anything special about the buffer letter in gülmeye?

Yes. After the verbal noun gülme, you’re adding a vowel-initial case ending (-e). Turkish inserts the buffer consonant -y- to prevent two vowels from clashing: gülme + e → gülmeye.